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Recognising the Symptoms of Heat Stroke and Sunburn
If you've been on a 40-degree fishing trip or stuck on a hot work site in late December, you've probably watched someone go quiet, sit down in shade, and not bounce back the way they should. That moment is when recognition matters. Heat-related illness puts thousands of Australians in emergency departments every summer. Severe sunburn drives a large share of those visits, but heatstroke is the more dangerous problem. The Australian Resuscitation Council classifies heatstroke as a medical emergency with a mortality risk if cooling and ambulance care are delayed.
If you're reading this because someone you're with looks unwell right now, skip to "When to call 000" first. The rest of this article covers how to recognise heatstroke and severe sunburn early, the point at which either becomes urgent, and the cooling steps to start before the ambulance arrives.
Heatstroke and heat exhaustion: the critical distinction
Heat illness sits on a spectrum: heat cramps, then heat exhaustion, then heatstroke at the dangerous end. The Australian Resuscitation Council defines heatstroke as a core body temperature above 40°C combined with central nervous system dysfunction (Guideline 9.3.4). Heat exhaustion is the milder condition that often precedes it. Both involve heat overload. Only heatstroke is a life threat.
Two patterns of heatstroke matter for first aiders:
Classic heatstroke develops slowly during prolonged heat exposure. It is most common in older people, infants, and anyone unable to escape the heat, for example, an upper-floor flat without air conditioning during a heatwave. Skin is usually hot, red, and dry.
Exertional heatstroke develops quickly during intense physical activity in hot conditions. It can affect healthy young adults including tradies, hikers, soldiers, and athletes. Skin may still be sweating despite a dangerously high core temperature. We have seen exertional cases on construction sites in regional Victoria where the casualty is still sweating freely, and that surface presentation hides how serious the internal picture has become.
The old rule of thumb that "if they have stopped sweating, it is heatstroke" is unreliable. Sweating during an exertional case does not rule out heatstroke. Mental state and core temperature are the better markers.
Signs that someone has heatstroke
These features all signal heatstroke, drawn from Australian Resuscitation Council guidance:
- Core body temperature above 40°C, where a thermometer is available
- Altered mental state: confusion, disorientation, slurred speech, difficulty answering simple questions
- Aggressive or out-of-character behaviour
- Seizures
- Loss of consciousness
- Skin that is hot to touch (typically red and dry in classic heatstroke; may still be sweating in exertional heatstroke)
- Rapid, weak pulse
- Rapid, shallow breathing
- Headache, dizziness, nausea, vomiting
A person can move from "looks a bit unwell" to "collapsed" inside fifteen or twenty minutes. If you suspect heatstroke, start cooling immediately and call 000. Do not wait for confirmation.
When heatstroke becomes a medical emergency
Three signs upgrade a hot, unwell person to an urgent ambulance call:
- Confusion or any altered consciousness
- Seizures
- Loss of consciousness
Any one of these alone is a 000 call. If you are alone with the casualty, call 000 first, then begin cooling.
How to recognise severe sunburn
Sunburn is sometimes treated as a cosmetic problem. It is not. Severe sunburn causes inflammation, fluid loss, and skin damage that lifts lifetime melanoma risk. Australia has the highest rate of skin cancer in the world, and most cases trace back to cumulative UV exposure starting in childhood.
Severity tends to move through three stages:
- Mild: pink to red skin, warm to touch, tender. No blisters. Resolves with cool water, fluids, and aftersun moisturiser over a few days.
- Moderate: deeper red, painful, sometimes swollen. Skin peels within three to seven days.
- Severe: blistering, intense pain, marked swelling. The burn area may feel hot beyond the visible burn line. Often accompanied by chills, fever, headache, or nausea.
UV damage starts the moment skin is exposed. Visible redness usually appears several hours after exposure and peaks the following day, so a burn that looks mild at the beach can be far worse by the next morning.
Sunburn signs that need medical care
Get a sunburn checked by a GP, or call Healthdirect on 1800 022 222, if it presents with any of these:
- Blisters covering more than around 20% of the body surface
- Fever, chills, or vomiting alongside the burn
- Severe pain or signs of infection (pus, expanding redness around blister edges, warmth)
- Confusion, dizziness, or extreme fatigue (suggests heat illness on top of sunburn)
- Sunburn in a baby under twelve months. Any sunburn at that age warrants medical advice.
Call 000 instead if the person is showing signs of heatstroke (confusion, seizures, loss of consciousness) on top of the burn.
What to do first
Recognition is step one. Rapid cooling is step two. While the ambulance is on the way, the Australian Resuscitation Council recommends:
- Move the person to a cool, shaded area
- Remove excess clothing
- Apply cool water to the skin by dousing, sponging, or laying wet sheets over the body
- Fan the skin to accelerate evaporative cooling
- Apply ice packs or instant cold packs to the neck, armpits, and groin
- Give small amounts of cool water only if the person is fully alert and able to swallow safely
For step-by-step treatment once heat illness or severe sunburn is confirmed, see our guide on how to treat heat stroke and sunburn. For home care of sunburn that does not need hospital attention, see treating sunburn.
What not to do
A handful of common mistakes can make heatstroke or severe sunburn worse:
- Do not put an unconscious or seizing person in a cold bath. The aspiration risk is real, and immersion makes airway management impossible.
- Do not give fluids by mouth to anyone who is not fully alert and able to swallow safely.
- Do not wait for the casualty to stop sweating before treating suspected exertional heatstroke. Sweating can continue in exertional cases.
- Do not apply butter, toothpaste, ice, or vinegar directly to severe sunburn. Cool water and aftersun gel only.
- Do not pop sunburn blisters. Intact blisters protect the skin underneath while it heals.
When to call 000
Call 000 for an ambulance any time a person shows:
- Confusion, slurred speech, or altered consciousness
- Seizures
- Loss of consciousness
- A measured core temperature above 40°C with any neurological symptom
- Severe sunburn covering a large body area with systemic symptoms such as fever, vomiting, or fainting
Heatstroke is time-critical. Cooling buys time. Definitive care happens in hospital, where the team can monitor for kidney injury, liver damage, and clotting problems that can follow even a textbook recovery.
Frequently asked questions
Can you get heatstroke without being in the sun?
Yes. Classic heatstroke develops in any hot environment, including closed cars, upper-floor flats without air conditioning, and industrial workplaces. Direct sun exposure is not required.
How long does sunburn take to appear?
UV damage begins immediately. Visible redness usually appears several hours after exposure and peaks the following day. Pain often worsens overnight.
Can you treat heatstroke at home?
No. Begin cooling and call 000. Cooling at the scene buys time, not recovery. The person needs hospital observation for organ damage.
What is the practical difference between heat exhaustion and heatstroke?
Heat exhaustion presents with heavy sweating, weakness, headache, and nausea, but mental state stays normal. Heatstroke adds altered mental state, possible seizures, and a core temperature above 40°C. Heat exhaustion can progress to heatstroke if it is not treated, so do not wait to act.
Is sunscreen enough on a 40°C day in regional Victoria?
Sunscreen helps but is not enough on its own. The Cancer Council's SunSmart advice combines five steps: slip on clothing, slop on SPF 50+ broad-spectrum sunscreen, slap on a wide-brim hat, seek shade, and slide on wraparound sunglasses. The SunSmart app shows the daily UV index, and UV 3 or above is enough to damage skin even on cool or cloudy days.
What to put in your kit for an Australian summer
The contents of an outdoor kit are settled by the question this article asks: can you recognise heat illness or severe sunburn, and can you act in the first few minutes? For a 40-degree camping weekend or a hot regional work site, the items that earn their place are instant cold packs, electrolyte sachets, aftersun gel, a digital thermometer that reads above 40°C, sterile dressings for blistered skin, and a charged phone within signal range. Our outdoor first aid kits are built around this kind of summer day. If you'd rather talk through what your kit needs for camping, fishing, or a regional work site, call our team in Bendigo on 03 5443 2239.