Heat, cold, bites and stings

The four emergencies in this lesson come from outside the body: heat, cold, something that stings and something that bites. They share a feature that makes them easy to get wrong. Each comes with a move that feels right: rub the cold limb, suck out the venom, pull the tick with a twist, cool the overheated runner in the ambulance on the way. Every one of those is ruled out by the guidelines or the public health pages behind them, and most of them for a reason you can learn in a sentence. And the most urgent action here isn't one most people would reach for.

You'll also meet a guideline saying "no recommendation", and read it with what lesson 4 taught you: a grade describes the evidence, not whether to act.

The US guidance is the AHA and American Red Cross's 2024 first aid guideline, which covers every topic in this lesson and grades each recommendation.¹ The UK guidance is RCUK's 2025 first aid guideline, the UK version of the European Resuscitation Council's, which covers heatstroke, snakebite and the prevention of hypothermia but has no section on frostbite, stings or ticks.²³ For those three, the UK texts in this lesson are the NHS and St John Ambulance pages.⁷⁹¹⁰ This lesson says so each time.

Too hot: two conditions, one line between them

Heat illness comes in two grades, and the whole of your response depends on which one you're looking at.

Heat exhaustion is the body coping, badly. The NHS lists tiredness, dizziness, a headache, feeling or being sick, heavy sweating with pale, clammy skin, cramps in the arms, legs and stomach, a high temperature, strong thirst and irritability.⁶ St John's list is much the same.¹⁰ The NHS says it does not usually need emergency help if the person can cool down within 30 minutes.⁶

Heatstroke is the body failing to cope. The AHA/Red Cross guideline defines it in its recommendation table as heat illness with altered mental status; RCUK says to suspect it in someone showing confusion, agitation, disorientation, seizures or unresponsiveness.¹² The European text adds a core temperature above 40 °C (104 °F), and says measuring one in first aid is a problem, because it takes a rectal thermometer: an ear reading is only an approximation, and mouth and skin readings are inaccurate, though a high reading on one can still support the suspicion.³ So for you, the practical line is the brain. A hot person who is confused, oddly agitated, fitting or not responding has heatstroke until someone with better tools says otherwise.

The line is not perfectly clean. St John's heat exhaustion list includes dizziness and confusion, and the NHS adds a clock: still unwell after 30 minutes of rest, cooling and fluids is on its call-999 list for heatstroke.¹⁰⁶ This course's reading: when the texts blur, treat confusion as heatstroke, because the guideline definitions do.

Heat exhaustion: cool, drink, watch

The two countries' steps are close.

• In the US: the guideline has no separate heat exhaustion recommendation. Its recommendation for exertional hyperthermia (a body overheated by exercise) or heatstroke says to move the person out of the heat, remove excess clothing, limit exertion, and give cool liquids if they are able to swallow (AHA/Red Cross 2024, COR 1, LOE C-EO).¹ For someone dehydrated by exertion, any rehydration drink or clean water will do, as long as there's no shock, confusion or trouble swallowing (COR 1, LOE C-LD), and a 4% to 9% carbohydrate-electrolyte drink, which is 4 to 9 g of carbohydrate in every 100 mL, is reasonable over plain water if both are to hand (COR 2a, LOE B-R).¹ The ILCOR reviews behind it found those drinks gave the best fluid balance overall.¹
• In the UK: the NHS gives four steps: a cool place, unnecessary clothing off, plenty of water (or an isotonic sports drink or rehydration salts), and cool skin, sprayed or sponged with cool water and fanned, with cold packs wrapped in a cloth under the armpits or on the neck. Then stay with them.⁶ St John adds lying down with the legs raised.¹⁰

The CDC's workplace page for heat cramps says, flatly, "Avoid salt tablets."¹¹ It gives no reason, so this course will not supply one. What it offers instead is water and a snack or a drink that replaces carbohydrates and electrolytes, every 15 to 20 minutes.¹¹

Confusion, a seizure, collapse, or no better after 30 minutes makes it heatstroke. The AHA's heatstroke recommendation still allows cool liquids if the person can swallow, and its rehydration recommendation leaves out anyone confused; the US National Weather Service is blunter, "Do NOT give fluids."¹¹² This course applies lesson 14's rule: nothing by mouth unless fully awake and able to swallow.

Heatstroke: cool first, transfer second

For heatstroke, both countries tell you to call and both tell you to cool, but cooling is not a comfort measure while you wait. It's the treatment.

In the US (AHA/Red Cross 2024):

• The call: call for anyone with heatstroke (COR 1, LOE C-EO)¹
• First: out of the heat, excess clothing off, exertion limited, cool liquids if able to swallow (COR 1, LOE C-EO)¹
• Best method: cool to cold water, neck down, 15 minutes or until thinking clears (COR 2a, LOE C-LD; children C-EO)¹
• No water: ice packs, cold showers, ice sheets and towels, cooling vests, fanning (COR 2a, LOE C-LD; children C-EO)¹
• Moving them: no order for transport given

In the UK (RCUK 2025, unless another text is named):

• The call: not in RCUK's steps; the ERC's text says call as cooling begins, and the NHS says 999[3]⁶
• First: out of the heat, excess clothing off, into shade[2]
• Best method: cold water, 1 to 26 °C, neck down: the "gold standard"²
• No water: ice sheets, ice packs, a fan, a cold shower, cooling vests, or mist and a fan[2]
• Moving them: cool first, transfer second, and keep cooling on the way (and ERC 2025)²³

The US method in the AHA's words: "For adults with heatstroke, it is reasonable to initiate immediate active cooling by using whole-body (neck-down) cool- to cold-water immersion for 15 minutes or until neurological symptoms resolve (whichever occurs first)." (AHA/Red Cross 2024, COR 2a, LOE C-LD)¹ RCUK's, for the UK: "The gold standard is to use whole-body (neck down) cold water (1-26°C) immersion until the core temperature falls below 39°C." Without a core temperature, "continue cooling for 15 min or until neurological symptoms resolve, whichever is first" (RCUK 2025).²³ 1 to 26 °C is about 34 to 79 °F; 39 °C is 102.2 °F. The two agree on nearly everything.

Underneath both is ILCOR's review. Its 2020 recommendation, for adults with exertional hyperthermia or exertional heatstroke: "We recommend immediate active cooling using whole body (neck down) water immersion techniques (1-26°C; 33.8-78.8°F) until a core body temperature of less than 39°C (102.2°F) is reached (weak recommendation, very low certainty evidence)."⁴ Its 2025 update lists heatstroke cooling among the topics with no new systematic or scoping review since 2020; there was an evidence update in 2022, and the 2020 recommendation stands.¹⁵

Why water, and why first

The guidelines give the evidence, not the physics: a body in water cooled fastest.⁴ Cooking Fundamentals lesson 2 gave you a reason to expect it: air hands heat to skin far more slowly than water does, which is why your arm survives a second in a 200 °C oven and not in boiling water. Run it the other way and a hot body loses heat to cold water far faster than to air. That connection is this course's; the first aid guidelines don't make it.

Speed matters because of what heatstroke does while it lasts. The AHA's supporting text says it can lead to muscle injury, bleeding problems, organ failure, collapse and death, and that survival is related to how fast the temperature comes down.¹ The European guideline gives a number: "A cooling rate of ≥0.15 °C /min has been shown to be associated with survival without medical complications for exertional heat stroke."³

How cold the water, and how long

Here the sources read the same evidence two ways. ILCOR's notes on the evidence say that, though cooling rates varied, colder water was associated with faster cooling.⁴ The AHA's supporting text, citing the same ILCOR review: "There was no significant difference in the rate of body temperature reduction across water temperatures of 2 to 26° C (36° F–79° F), indicating that the act of immersion, rather than water temperature, is most important."¹ Neither changes what you do: use whatever water you have, at 26 °C (79 °F) or below.

Without a thermometer you can't know when they are below 39 °C, and a lay first aider will not usually have one: the AHA grades measuring core temperature as something trained and willing providers may do (COR 2b, LOE C-EO).¹ So both countries give the same stopping rule: 15 minutes, or until the confusion clears, whichever comes first.¹² It is a rule for when nobody can measure, not a claim that 15 minutes is always enough. ILCOR says the right time is not known and chose 15 minutes because benefit was more plausible than harm, and the ERC and RCUK say to keep cooling during transport.²³⁴

Lesson 10 warned you against chilling a burned child's whole body under cold water. Here chilling the whole body is the point, because the core is dangerously hot.

The public pages

The UK public pages don't mention immersion. The NHS page, last reviewed on 28 May 2026, says: "Wrap the person in a cool, wet sheet, or fan them or sponge them down with cold water while you wait for help to arrive."⁶ St John's heatstroke page, clinically reviewed on 28 April 2025, teaches the wet sheet too, with cold packs in the armpits and around the neck.¹⁰ RCUK's October 2025 guideline calls immersion the gold standard and lists a fan and ice sheets among its alternatives.² In the US, the CDC's workplace page lists a cold water or ice bath, if possible, first, and the National Weather Service's first line for heatstroke is to call 911 or get the person to a hospital immediately.¹¹¹² Where there is water and help to put someone in it, immersion is what the guidelines grade best; where there isn't, the wet sheet and fanning are what you have. Neck down means the head stays out, and someone stays with them throughout. This course's reading, as in the second case below, is that you don't wrestle someone who can't stand into a bath.

The finish line in Knoxville

A half-marathon in Knoxville, Tennessee, on a humid morning. A runner in her twenties crosses the line, sways, and sits down hard. She's flushed, still sweating, and when you ask her name she gives it, then asks twice where she is and argues that she has not finished yet. The medical tent is 50 metres away and has a tub of iced water.

Which one. She's confused. That's heatstroke, not exhaustion, whatever her skin is doing (AHA/Red Cross 2024).¹ Sweating does not rule it out: the CDC lists hot, dry skin or heavy sweating among its signs.¹¹

Call. Make sure 911 is called, by you or the race medics (AHA/Red Cross 2024, COR 1).¹

Cool, now. She goes into the tub, neck down, with the medics, for 15 minutes or until she is thinking clearly (AHA/Red Cross 2024, COR 2a).¹ No drink while she's confused (lesson 14's rule; the NWS says no fluids for heatstroke).¹²

Then transfer. The crew takes her once she is cooled or cooling. Nobody loads her into the ambulance first to cool her on the way, which is the order the ERC and RCUK rule out ("cool first, transfer second", ERC 2025; RCUK 2025); the US guideline's "immediate" cooling points the same way.¹²³

If she stops responding. Normal breathing is quiet and regular at an ordinary pace; slow, noisy, gasping or irregular breathing is not normal. If she stops responding and is not breathing normally, it's cardiac arrest (lesson 2): out of the water, CPR, the call handler coaching, and an AED. If she stops responding but is breathing normally, she comes out of the tub into lesson 7's recovery position, and cooling carries on with wet towels and ice packs.

A heat wave, and an older neighbour

The runner is the case the evidence is about. The European guideline describes the other kind, classic or non-exertional heatstroke: it typically comes after long exposure to the sun, often in heat waves, and in people whose temperature control is weaker, such as older people or children.³ ILCOR looked for evidence on cooling them and found none:⁴

• For adults with classic heatstroke, ILCOR cannot make a recommendation for or against any specific cooling technique (no recommendation, very low certainty evidence).
• The same for children with either kind.

"No recommendation" does not mean cooling does not matter or that immersion is wrong. It means nobody has compared the methods in these people. You met the same words about suction devices in lesson 8. The European text reads the gap this way: there are no studies in children or in non-exertional heatstroke, but it says the evidence from ILCOR's review supports rapid cooling by similar methods in them too. That is the ERC's reading, not ILCOR's.³ RCUK's step doesn't say exertional: for any suspected heatstroke it says to use whatever cooling is to hand.²

In Peterborough, during a heat wave, you let yourself into your 81-year-old neighbour's top-floor flat because he has not answered the door since yesterday. The rooms are stifling. He is sitting in a chair, hot to the touch, muddled about what day it is, and he can't stand up without help. The flat has a shower over a bath, no ice, and no thermometer.

You've recognised heatstroke from his confusion, and you've called 999 on speaker.

Too cold: hypothermia

The NHS defines hypothermia as a dangerous drop in body temperature below 35 °C (95 °F), against a normal of about 37 °C.⁷ Its signs include shivering, pale, cold, dry skin, blue or grey skin and lips, slurred speech, slow breathing and tiredness or confusion; a baby may be cold to the touch, floppy, quiet and not feeding.⁷

The AHA's table sorts hypothermia into stages by core temperature, which you will not have, and gives the signs of each.¹ Cold stress: alert, perhaps shivering. Mild: shivering, and a change in how responsive they are. Moderate: less responsive, shivering or not, pale skin, sometimes with frostbite; the table calls this a medical emergency. Severe: unresponsive, perhaps looking lifeless, shivering stopped, slow heart rate and breathing. This course's reading of that table: a person who has stopped shivering is not necessarily getting better, and anyone who is less responsive than they should be gets the moderate treatment, which is the call and gentle handling.

Most of the response is the same in both countries.

In the US (AHA/Red Cross 2024):

• Stop the heat loss: somewhere warm, soaked clothes off, blankets, and active rewarming if you have the means (COR 1, LOE B-R)¹
• Can't move them: insulate from the ground, cover head and neck, a plastic or foil layer against the wind plus a dry layer (COR 1, LOE C-LD)¹
• The call: call if they are less responsive, mumbling, confused, can't help undress, pale, blue-tinged or frozen skin (COR 1, LOE C-EO)¹
• Food and drink: for cold stress or mild hypothermia only, high-calorie food or drink if alert and able to swallow (COR 1, LOE C-EO)¹
• Heat packs and bottles: allowed, with insulation from the skin, the maker's instructions, and checks for burns and pressure injury (COR 1, LOE C-LD)¹

In the UK:

• Stop the heat loss: indoors or sheltered, wet clothes off, a blanket, sleeping bag or dry towel, head covered (the NHS)⁷
• Can't move them: shelter from wind, a thick dry layer underneath, blankets or a sleeping bag, a foil blanket (St John)¹⁰
• The call: A&E or 999 for suspected hypothermia (the NHS); 999 or 112, and never leave them alone (St John)⁷¹⁰
• Food and drink: a warm non-alcoholic drink and sugary food, only if fully awake (the NHS) or fully alert (St John)⁷¹⁰
• Heat packs and bottles: no hot water bottle, heat lamp or hot bath (the NHS); no direct heat, because of burns (St John)⁷¹⁰

Active rewarming means applying heat to the body from outside, such as a heat pack; passive rewarming means stopping the heat loss and letting the body warm itself.¹ RCUK's list is for preventing hypothermia: insulation, protection from wind, wet clothing gently removed and replaced with dry, and insulation from the ground (RCUK 2025).²

Three things differ. The AHA allows a heat source with insulation under it and watches the skin, where the NHS rules the bottle out and St John rules out direct heat for its burn risk. The AHA rules out a warm bath only once responsiveness is reduced; the NHS says no hot bath at all. And St John suggests your own body to keep them warm, which the AHA grades no better than other active methods (3: No Benefit).¹⁷¹⁰

Handle them gently, and leave the limbs alone

The AHA's table of hypothermia stages says to handle a moderately hypothermic person gently.¹ It does not say why in that line, and this course will not add a reason of its own. RCUK's list says to remove wet clothing gently, too.² The ERC's flowchart for professionals gives one for moderate and severe hypothermia: "Minimal and cautious movements to avoid rescue collapse" (ERC 2025).¹⁴ The passages this course read don't define rescue collapse, so neither will this lesson.

Two things are graded as harmful, and here the AHA does give its reasons.

• "Heat sources, rubbing, and massage should not be applied to the extremities of a person with hypothermia." (AHA/Red Cross 2024, COR 3: Harm, LOE B-NR)¹ The NHS says the same: don't rub their arms, legs, feet or hands.⁷
• A warm shower or warm bath is potentially harmful for someone whose responsiveness is reduced (COR 3: Harm, LOE C-LD), because of the risk of the core temperature dropping further, low blood pressure, falls and drowning.¹

On alcohol, the NHS says not to give it, and St John says "it will make hypothermia worse", without giving a mechanism.⁷¹⁰

On your own body:

• In the US: body-to-body warming is no better than other active methods (AHA/Red Cross 2024, 3: No Benefit, LOE C-LD).¹
• In the UK: St John says you can use your own body to shelter them and keep them warm, but not to give them your clothes, because you need to stay warm yourself.¹⁰

If they stop responding. Breathing normally, quietly and regularly: lesson 7's recovery position, blankets over and under, and keep watching. Not breathing normally: lesson 2, the call and CPR. The AHA/Red Cross hypothermia recommendations above don't apply to cardiac arrest (or to babies under 60 days old), so the rule for an arrest comes from the resuscitation guidelines.¹ Read at the source, nothing in them changes lesson 2 for a lay rescuer with a cold person. Here is what they say, and who each line is for.

• In the US: "full resuscitative measures should be performed immediately and continued concurrently with rewarming" for anyone with life-threatening hypothermia and no obvious lethal injury (AHA 2025, COR 1; LOE C-LD for adults, C-EO for children).¹⁵ The AHA writes this guideline "primarily for North American health care professionals", and no hypothermia line in it is marked for lay rescuers.¹⁵ For you, this one means lesson 2's CPR, started now. The rewarming it pairs with CPR, and the rest of its list (shocks, drugs, machines that take over the heart and lungs, which hospital), are for the crew and the hospital.
• In the UK and Europe: the ERC's guide for the public says "Hypothermic persons in cardiac arrest should receive continuous CPR until warming has been re-established", with compressions and breaths at the standard rate from your training, and says to protect them from the cold (ERC 2025).¹⁶ For you, that is lesson 2's CPR until the ambulance crew take over.

The professional texts say three more things you may hear about. None is a step for you.

• The one-minute check. RCUK's special circumstances guideline says "Check vital signs for up to 1 min in an unconscious hypothermic patient." (RCUK 2025, ungraded), and the ERC's says the same with "one minute" (ERC 2025, ungraded).¹⁷¹⁴ Vital signs there are pulse and breathing, the ERC's supporting text does the check with heart monitoring and ultrasound as well as by examination, and the ERC's guide for the public leaves the line out.¹⁴¹⁶¹⁷ This course's reading is that the line is written for professionals, so it doesn't teach you a longer check. Slow breathing is one of the NHS's signs of hypothermia, and RCUK counts slow, laboured breathing in an unresponsive person as a sign of cardiac arrest (RCUK 2025), which is one more reason the UK call comes first: the call handler helps you decide.⁷¹⁷
• Delayed or stop-start CPR. The AHA says it "may be reasonable" when standard CPR isn't possible because of the conditions, to get the person out quickly (AHA 2025, COR 2b, LOE C-EO); RCUK and the ERC allow it when the core temperature is below 28 °C (82.4 °F) and continuous CPR isn't feasible (RCUK 2025; ERC 2025).¹⁵¹⁷¹⁴ That takes a low-reading thermometer you won't have and a rescue team's judgement. Your part is lesson 2's: check it's safe for you first, which the AHA also stresses for a hypothermic arrest.¹⁵
• When to stop. The AHA says severe hypothermia can produce "findings that mimic death", and "Apparent rigor mortis or fixed dilated pupils may not be reliable signs of death in this setting."¹⁵ It adds that cold lowers the body's metabolism and oxygen use, which improves the chance of survival and recovery even after a long arrest.¹⁵ Its list of conditions for withholding CPR is in the supporting text of a guideline written for professionals, and the ERC's flowchart for professionals says "Do not terminate CPR" on the way to a hospital that can rewarm.¹⁵¹⁴ So cold and stiff is not a reason for you to stop: keep going until the crew take over.

Frostbite

Frostbite is skin, and sometimes the tissue beneath it, freezing. The AHA's background says ice crystals form inside the cells, and that the fingers, toes, nose and ears are particularly susceptible.¹ The NHS says it can happen at 0 °C (32 °F) or below, and that the skin may first be cold and firm, numb, stinging or burning, painful, and red or pale; worse, it's hard, white, blue or blotchy, with swelling, loss of feeling and blisters.⁷

Rewarm, but only once. Two COR 1 recommendations work together (AHA/Red Cross 2024, both LOE C-LD):¹

• "The preferred method for warming frostbitten tissue is clean lukewarm water immersion at 37°C to 40°C (99°F–104°F)."
• "Frostbitten tissue should be rewarmed at the earliest opportunity, as long as there is no risk of refreezing."

The mechanism is in the supporting text. The damage comes from ice crystals destroying cell membranes, so tissue that thaws and freezes again is harmed again, and experts recommend strictly avoiding refreezing.¹ Hotter is not better: in one animal study, rewarming in 45 °C (113 °F) water was harmful.¹ With no thermometer, the text says to test the water on your wrist, where it should feel slightly warmer than your body.¹ If lukewarm water is not possible, let it rewarm in warm room air or against the person's own warm skin (COR 1, LOE C-LD).¹

The rest of the US list is all COR 1: prompt medical attention; rings and anything tight off, because the tissue will swell; for someone with moderate to severe hypothermia, warm the core before treating the frostbite, because warming the limbs first can drop the core temperature; protect the part and avoid walking on frozen feet; and loose, bulky, clean, dry dressings, including between the toes and fingers.¹ The walking rule has its own reason: frozen tissue can't feel damage being done to it.¹ Ibuprofen may be reasonable (2b), and blisters are not for first aiders to break (3: No Benefit).¹

In the UK, RCUK's guideline has no frostbite section. The NHS page: shelter, jewellery, gloves and boots off, warm the part in an armpit or a lap, then in warm (not hot) water, dry it, a light dressing, raise it, and 999 or A&E for hard frozen skin, swelling and numbness, or blisters. No rubbing, no fire, radiator, hot water bottle or heat lamp, no hot bath, no alcohol.⁷ St John gives the water as around 40 °C and says rubbing could damage the skin.¹⁰ Neither UK page mentions refreezing; the AHA's rule is the one that decides the case where help is far away.

Bee and wasp stings

Most stings are a small, painful, swollen, itchy lump. The AHA puts deaths from bees, wasps and hornets at about 60 a year in the US, mostly from anaphylaxis.¹ Anaphylaxis from a sting is lesson 13: adrenaline first, the call, and in the UK lying down. The AHA's sting recommendations start with the three from it: the person uses their auto-injector, you help if needed, and the call (COR 1).¹ What's left is the sting itself, and the countries differ on one detail.

The difference is how the stinger comes out, and each side gives its reason. The NHS's is that tweezers could squeeze poison out of it. The AHA's is a study in volunteers: plucking and scraping made no difference to the size of the welt, but the welt grew with the time the stinger stayed in; its background says a honeybee's barbed stinger, which often stays in the skin, can keep delivering venom for up to 60 seconds.¹ So in the US reading, speed matters and method does not; in the UK reading, method matters. Both allow a fingernail scrape. Other bees, wasps and hornets have smooth stingers and can sting again and again (the AHA).¹

When a sting is more than a sting. The NHS's 999 list for a bite or sting is lesson 13's anaphylaxis list: swelling of the lips, mouth, throat or tongue, fast or difficult breathing, a tight throat, blue or grey skin, sudden confusion or drowsiness, someone who faints and can't be woken.⁹ It sends someone who was stung more than once, or who has reacted badly before, to an urgent GP appointment or 111.⁹

Ticks

A tick is a small, spider-like creature that attaches to skin and feeds on blood for days.⁹ Some carry infections: the AHA names Lyme disease and Rocky Mountain spotted fever in the US.¹ The NHS says ticks that may carry Lyme disease are found all over the UK, with grassy and wooded areas in southern England and the Scottish Highlands among the high-risk places.⁹

Here the two countries agree almost word for word.

• Remove it as soon as possible (AHA/Red Cross 2024, COR 1, LOE B-NR).¹ The AHA's text says the risk of infection rises with the time the tick is attached, and appears more substantial after 24 to 48 hours.¹
• How: grasp the head of the tick as close to the skin as possible with tweezers or a tick-removal tool and pull upward with steady, even pressure (AHA/Red Cross 2024, COR 1, LOE C-LD).¹ The NHS: fine-tipped tweezers or a tick-removal tool, as close to the skin as possible, and pull slowly upwards without squeezing or crushing the tick.⁹
• Then clean the bite with soap and water or antiseptic (the NHS).⁹

The CDC's page adds the don'ts. Don't twist or jerk, because the mouthparts can break off in the skin; if they do and will not come out easily, leave them for the skin to push out. Don't use petroleum jelly, heat, nail polish or anything else to make it let go, which the CDC says may agitate the tick and force infected fluid into the skin.¹³ The AHA's text says those methods, and a hot match, appear less effective than pulling it out.¹ Don't crush it in your fingers.¹³

Afterwards, the two countries give different advice.

• In the US: the AHA says a tick bite in a region with a lot of Lyme disease should be discussed with a health professional within 72 hours of removing an engorged tick, one swollen with blood (COR 1, LOE B-R); trials found a single antibiotic dose in that window, after a bite from the blacklegged tick, could prevent Lyme disease.¹ The CDC says see a doctor for a rash or fever in the weeks after.¹³
• In the UK: the NHS says ask for an urgent GP appointment or call 111 if, within 3 months of a bite or of being somewhere with infected ticks, you have flu-like symptoms or a round or oval rash.⁹

Snakebite

Snakebite has the most folk remedies of anything in this lesson, and both countries rule them out.

On what you do, the two agree: call, keep still, take off anything tight, and none of the rest. What differs is the snakes they are written for, which is the whole story of the pressure bandage.

The AHA says its recommendations are for the United States and Canada and their native snakes, and that snakes elsewhere have different venom and may need different first aid.¹ More than 95% of venomous bites in North America are from pit vipers, the rattlesnakes, copperheads and cottonmouths, whose venom injures tissue and can cause low blood pressure and bleeding.¹ RCUK's is for the UK, where the only native highly venomous snake is the adder, whose venom it describes as haemolytic, meaning it damages the blood.² The NHS describes the adder as grey or reddish-brown with a dark zigzag stripe down its back, and says most UK bites are not serious but all need checking.⁸

Why keep still? The AHA's text reports a study in which fluid injected under the skin moved faster when the person walked for 10 minutes or more, which could mean more venom absorbed; it says to balance less exertion against getting to care without delay.¹ RCUK's reason is the same idea in one clause.²

Why no pressure bandage. You may have heard that a tight bandage is the right first aid for a snakebite. For some snakes it is. The European guideline explains the split: bites from elapids, a snake family with non-swelling venom that attacks the nerves, may benefit from pressure immobilisation, but viper bites need simple immobilisation without compression; it names the adder as a viper.³ The AHA's reasons for North America: studies of pressure bandages are mixed on benefit and on harm, including worse tissue injury; medical staff and lay rescuers rarely put one on correctly; and though a well-placed one may have a role in bites with nerve-acting venom, more than 95% of the continent's bites are from pit vipers.¹ The US does have elapids, the coral snakes, and the AHA's rule still covers them.¹ This course has not read a guideline from a country where elapid bites are common, so it teaches neither the bandage nor its technique.

The NHS adds two lines worth knowing: paracetamol for pain, but not aspirin or ibuprofen, because they can make bleeding worse; and remember the snake's colour and pattern, or photograph it from a distance if it's safe, without going near it.⁸

What people get wrong

"Get them to hospital, they can cool them there." Cool first, transfer second (ERC 2025; RCUK 2025); survival is related to how fast the temperature comes down (AHA/Red Cross 2024).¹²³

"No sweat, no heatstroke." Hot skin without sweating is on the NHS's list, but the CDC lists hot, dry skin or heavy sweating, and the runner in Knoxville was sweating.⁶¹¹ Confusion is the sign the AHA and RCUK define it by.¹²

"A drink will sort them out." Not while they're confused. The AHA allows cool liquids only if the person can swallow, the NWS says no fluids for heatstroke, and this course's rule is nothing by mouth unless fully awake.¹¹²

"Alcohol warms you up." Don't give it; St John says it makes hypothermia worse.⁷¹⁰

"Rub the cold limbs." Rubbing and heat on the limbs of a hypothermic person are COR 3: Harm (AHA/Red Cross 2024), and the NHS and St John both say not to rub frostbite; St John's reason is that it could damage the skin.¹⁷¹⁰

"Thaw frostbite right away, whatever happens next." Only if it will not refreeze (AHA/Red Cross 2024, COR 1).¹

"Suck out the venom," "cut it," "tie it off." All ruled out in both countries.¹²

"A tight bandage is the snakebite treatment." Not for vipers, and not under either country's guidance.¹²³

"Burn the tick off" or "smother it." Pull it out with tweezers, steadily.¹¹³

Practice

Where to learn more with your hands

Nothing in this lesson needs a manikin except the CPR any of it can end in. For that, keep practising with the BHF's RevivR or RCUK's Lifesaver between classes; a class near you is lesson 16's subject. The St John heatstroke, heat exhaustion and frostbite videos have not been watched against the guidance, and the heatstroke one teaches the wet sheet, so none is embedded. The NHS heat page, the NHS snakebite page with its photographs of the adder and the two harmless UK snakes, and the CDC's tick removal page show what the words describe. No adder photograph has been checked for its licence here, so the lesson describes it in words.

Connections

Cooking Fundamentals lesson 2's oven and boiling-water arithmetic is this course's explanation of why cold water wins for heatstroke. Lesson 10 cooled a burn and warned against chilling a child; here the whole body goes into cold water on purpose. Lesson 4's grading key is how to read ILCOR's "no recommendation" for classic heatstroke, and lesson 13 handles any sting that becomes anaphylaxis. Lesson 14's rule, nothing by mouth unless fully awake, holds for the confused runner and the mumbling hiker, and lesson 2 and lesson 7 decide what happens if either stops responding.

Go deeper

• Hewett Brumberg and colleagues, 2024 AHA and American Red Cross Guidelines for First Aid, Circulation, free: the environmental emergencies section, with the hypothermia stages table and the reasoning behind each snakebite row. Read in full here from an archived copy.
• ILCOR, First Aid Cooling Techniques for Heat Stroke and Exertional Hyperthermia,
  2020. How a recommendation is built from studies done mostly in healthy volunteers, and why it declined to recommend anything for classic heatstroke. Read in full.
• Djärv and colleagues, European Resuscitation Council Guidelines 2025 First Aid, Resuscitation: the heatstroke and snakebite sections, with the full list of cooling methods in order. Read in full on the publisher's page.
• NHS, Insect bites and stings. Stingers, ticks and caterpillar hairs, and when a bite needs a pharmacist, a GP or 999. Read in full.

Sources

1. E. K. Hewett Brumberg, M. J. Douma and colleagues, "2024 American Heart Association and American Red Cross Guidelines for First Aid", Circulation 150, 2024, e519 to e579. Read level: full, direct, from the Internet Archive capture 20260329073336, for all prose; the environmental emergencies section re-read on 2026-09-25. The recommendation tables for bee and wasp stings (Table 26), tick bites (Table 27), snakebite (Table 29), hypothermia (Table 32), frostbite (Table 33), heatstroke (Table 34) and oral rehydration (Table 35) were read from the table images; Tables 29, 32, 33, 34 and 35 were checked against the publisher's own images on 2026-09-24, and Tables 26, 27, 32 and 33 re-read from archived copies of those images on 2026-09-25.
2. Resuscitation Council UK, 2025 Resuscitation Guidelines: First aid, 27 October 2025 . Read level: full, direct; the "Prevention of hypothermia", "Heat stroke" and "Snake bite" sections re-read on 2026-09-25. It has no frostbite, sting or tick section.
3. T. Djärv, J. Rogers, F. Semeraro and colleagues, "European Resuscitation Council Guidelines 2025 First Aid", Resuscitation 215 (suppl 1), 2025, 110752 . Read level: full, direct, on the publisher's page; the hypothermia, heatstroke and snakebite sections re-read there on 2026-09-25.
4. ILCOR First Aid Task Force, First Aid Cooling Techniques for Heat Stroke and Exertional Hyperthermia, Consensus on Science with Treatment Recommendations, 2019 November (the 2020 CoSTR). Read level: full, direct; re-read on 2026-09-25.
5. T. Djärv, M. J. Douma and colleagues for the ILCOR First Aid Task Force, "2025 International Consensus on First Aid Science With Treatment Recommendations", Circulation 152, 2025. **Read level: full, direct, from the accepted manuscript on ilcor.org**; used here only for its list of topics not reviewed since 2020, which includes heatstroke cooling and pressure immobilisation for snakebite.
6. NHS, Heat exhaustion and heatstroke, last reviewed 28 May 2026 . Read level: full, direct; re-read on 2026-09-25.
7. NHS, Hypothermia, last reviewed 9 June 2023, and Frostbite, last reviewed 9 June 2025. **Read level: full, direct**; both re-read on 2026-09-25.
8. NHS, Snake bites, last reviewed 17 July 2026. **Read level: full, direct**; re-read on 2026-09-25.
9. NHS, Insect bites and stings, last reviewed 1 June 2023, and Lyme disease, last reviewed 3 June 2025 . Read level: full, direct, both read on 2026-09-25.
10. St John Ambulance, Heatstroke, Heat exhaustion, Hypothermia and Frostbite, each clinically reviewed 28 April 2025 . Read level: full, direct; all four re-read on 2026-09-25.
11. CDC, National Institute for Occupational Safety and Health, Heat-related illnesses. **Read level: full, from the Internet Archive capture 20260920095527**; re-read on 2026-09-25.
12. US National Weather Service, Heat Cramps, Exhaustion, Stroke. **Read level: full, direct**; re-read on 2026-09-25.
13. CDC, What to do after a tick bite, 9 June 2026 . Read level: full, from the Internet Archive capture 20260919133937, read on 2026-09-25.
14. C. Lott, V. Karageorgos, C. Abelairas-Gomez and colleagues, "European Resuscitation Council Guidelines 2025 Special Circumstances in Resuscitation", Resuscitation 215 (suppl 1), 2025, 110753 . Read level: full, direct, on the publisher's page, for the accidental hypothermia concise guideline, its evidence section and Fig. 5, read on 2026-09-25. A corrigendum (2026) has not been read.
15. D. Cao, A. M. Arens, S. L. Chow and colleagues, "Part 10: Adult and Pediatric Special Circumstances of Resuscitation: 2025 American Heart Association Guidelines", Circulation 152 (suppl 2), 2025. Read level: full, from the Internet Archive capture 20251027153841, for the scope and the hypothermia section (introduction, both recommendation tables and their supporting text), read on 2026-09-25.
16. European Resuscitation Council, The ERC Guidelines 2025 on Resuscitation for Everyone, lay guide, December 2025 . Read level: full, direct, for the special circumstances introduction and the hypothermia passage, re-read on 2026-09-25.
17. Resuscitation Council UK, 2025 Resuscitation Guidelines: Special circumstances and Adult basic life support, both 27 October 2025 . Read level: full, direct, for the accidental hypothermia section and the recognition of cardiac arrest, read on 2026-09-25.