"Sun poisoning" is not a medical diagnosis and nothing has actually poisoned you. It is the everyday name for a sunburn severe enough to make you systemically ill — fever, chills, nausea, headache, dizziness — or for a rash reaction to sunlight. Either way, the distinction that matters is simple: an ordinary sunburn affects your skin; sun poisoning makes you feel ill all over, and that is the point at which you should be assessed by a doctor.
If someone has confusion, fainting, a very high temperature, hot dry skin with no sweating, or a rapid weak pulse, treat it as a medical emergency and call emergency services. Those are signs of heat stroke, which is life-threatening.
Symptoms: ordinary sunburn versus sun poisoning
| Ordinary sunburn | "Sun poisoning" (severe reaction) |
|---|---|
| Red, warm, tender skin | Deep redness with extensive blistering |
| Mild swelling | Significant swelling, sometimes of the face or limbs |
| Peeling after 3–8 days | Fever and chills |
| Discomfort, itching | Nausea, vomiting |
| No systemic symptoms | Headache, dizziness, faintness |
| Rapid pulse, rapid breathing | |
| Confusion or disorientation | |
| Dehydration: intense thirst, dark urine, dry mouth | |
| Sometimes an itchy bumpy rash or hives on sun-exposed skin |
The rule of thumb: skin-only means sunburn; skin plus how you feel means seek help.
What is actually happening
Three different things get lumped under one label.
1. Severe sunburn. Extensive ultraviolet injury triggers a large inflammatory response. Cytokines released from damaged skin act on the whole body, producing fever, chills and malaise — the same mechanism that makes you feel wretched with an infection. Fluid also shifts into the burned tissue, which is why serious sunburn dehydrates you.
2. Heat illness alongside the burn. Sun exposure severe enough to burn usually comes with hours of heat load. Heat exhaustion — sweating, weakness, nausea, headache, clammy skin — often accompanies bad sunburn, and heat stroke is its dangerous escalation.
3. A photosensitivity reaction. Some people react to sunlight with a rash rather than a simple burn:
- Polymorphic light eruption — itchy red bumps or patches on sun-exposed skin, usually hours to a day after the first strong sun of the season. Common and generally not dangerous, though it recurs.
- Drug-induced photosensitivity — certain antibiotics (tetracyclines, some sulfonamides), diuretics, NSAIDs, retinoids, some antifungals and others sharply increase UV sensitivity. A dose of sun you have tolerated for years can produce a severe burn on a new medication.
- Photosensitive conditions such as lupus, porphyria or solar urticaria.
These need different management, which is another reason a proper assessment beats self-treatment when symptoms go beyond the skin.
When to get medical help
Emergency — call emergency services:
- Confusion, disorientation, slurred speech, seizures or loss of consciousness
- Temperature above 40 °C / 104 °F
- Hot, dry skin with no sweating
- Rapid weak pulse, difficulty breathing
- Persistent vomiting preventing fluid intake
Same-day medical assessment:
- Blistering over a large area — roughly more than one arm's worth — or blistering on the face, hands, feet or genitals
- Fever or chills after sun exposure
- Severe pain not relieved by over-the-counter analgesia
- Signs of dehydration: dizziness on standing, very dark or absent urine
- Any sunburn in an infant under one year old
- Sunburn while taking a known photosensitising medication
- A rash rather than a plain burn, particularly if it recurs
- Signs of infection: spreading redness, warmth beyond the burn edge, yellow discharge, red streaks, or pain that worsens after day two
If you are unsure, get it checked. Severe burns are undertreated far more often than overtreated.
What to do while arranging care, or for a milder case
- Get out of the sun and into a cool place — this comes before everything else.
- Rehydrate. Water, or an oral rehydration solution if there has been vomiting or heavy sweating.
- Cool the skin. Cool (not ice-cold) showers or damp compresses for 10–15 minutes at a time. No ice directly on skin.
- Moisturise while damp with a plain, fragrance-free lotion or aloe gel.
- Consider an oral NSAID such as ibuprofen for pain and inflammation, following the label and any advice specific to your medical history.
- Leave blisters intact. If one bursts, clean gently and cover loosely.
- Stay completely out of the sun until it has healed.
Avoid: petroleum jelly or heavy oils on a fresh burn (they trap heat); benzocaine or lidocaine sprays (contact allergy risk on damaged skin); popping blisters; peeling skin off deliberately; alcohol; and hot showers.
How long it takes
Systemic symptoms — fever, chills, nausea — usually settle within 24 to 48 hours once you are out of the sun and rehydrated. The skin follows the normal burn timeline: peak discomfort at 12–24 hours, peeling from day three to day eight, and, for blistering burns, one to two weeks or more with a risk of scarring and lasting pigment change.
If systemic symptoms are still present after 48 hours, or worsening at any point, that is a reason to be seen rather than to wait it out.
Preventing the next one
Severe reactions are almost always a dose problem, and the dose problem is almost always a timing problem — because sunburn is invisible while it is happening. Erythema takes two to six hours to appear, so nothing tells you to stop while it still matters.
Practical prevention:
- Check the live UV index for the hour you will be outside, not the temperature and not the forecast peak.
- Know your Fitzpatrick skin type and the burn time it implies at that index — the spread between types is roughly five-fold.
- Check your medicine cabinet. If you have started a new medication, look up whether it is photosensitising before a long day outdoors.
- Set a timer. Judgement fails precisely because the feedback arrives hours late.
- Rehydrate as you go, particularly in heat.
That is the loop Sunlit automates: live UV index for your coordinates, a personal limit derived from your skin type and applied SPF, and a session timer with sunscreen reapplication alerts — so the stopping decision is made in advance rather than the next morning. Free on iPhone and iPad.
Related reading
- How Long Does a Sunburn Last? The Hour-by-Hour Timeline
- How to Tan Without Burning: A Step-by-Step Method
- Fitzpatrick Skin Types: How to Find Yours and What It Means
This article is general information and does not replace medical assessment or advice. "Sun poisoning" describes several distinct conditions that need different treatment, and severe sunburn, heat exhaustion and heat stroke can all be dangerous. If you have any of the warning signs listed above, seek medical care. Sources: American Academy of Dermatology public guidance on sunburn; NHS guidance on sunburn and heat exhaustion/heat stroke; CDC guidance on heat-related illness; published reviews of polymorphic light eruption and drug-induced photosensitivity.
