Sun poisoning looks like an intense, deep red rash that progresses to blisters, noticeable swelling, and skin that appears inflamed well beyond a typical sunburn. Unlike a mild sunburn that simply turns pink and fades, sun poisoning produces visible changes that worsen over the first 24 to 72 hours and are often accompanied by whole-body symptoms like fever and chills.
The term “sun poisoning” isn’t a formal medical diagnosis. It’s a catch-all that covers two situations: a severe sunburn intense enough to cause systemic illness, and a separate allergic-type skin reaction to UV light called polymorphous light eruption. They look different from each other, and both look distinctly different from ordinary sunburn.
Severe Sunburn vs. Sun Poisoning on the Skin
A standard mild sunburn turns the skin pink or red, feels warm to the touch, and hurts when you press on it. These symptoms typically start fading within about three days. Sun poisoning starts with that same redness but keeps escalating. The skin becomes deeply red or even purplish, and the affected area swells visibly. Within hours to a day or two, fluid-filled blisters form on the surface, sometimes covering large patches of skin.
The blisters are a key visual marker. In a regular sunburn, the skin might peel as it heals, but it rarely blisters. In sun poisoning, blisters can range from small, scattered spots to large, raised pockets of fluid across the shoulders, chest, back, or wherever the exposure was worst. The surrounding skin often looks tight and shiny from swelling. Pain is significantly more intense and lasts longer than a normal sunburn.
Polymorphous Light Eruption
The other form of sun poisoning looks completely different from a severe burn. Polymorphous light eruption (often called PMLE or “sun allergy”) produces a rash of dense clusters of small bumps, raised rough patches, or tiny blisters packed closely together. The rash is typically very itchy rather than purely painful, which sets it apart from a sunburn right away.
Because “polymorphous” means many forms, this rash varies from person to person. Some people develop pinpoint bumps that look almost like hives. Others get patches of inflamed, textured skin that resemble eczema. The rash usually appears on areas that don’t get regular sun exposure, like the chest, arms, or lower legs, often within hours of being in the sun. It tends to be more common in spring or early summer when skin hasn’t adjusted to UV exposure yet. People with lighter skin are more susceptible, though it occurs across all skin types.
Symptoms Beyond the Skin
What truly separates sun poisoning from a bad sunburn is what happens to the rest of your body. Severe sun poisoning can trigger fever, chills, nausea, vomiting, headache, dizziness, and a general feeling of being ill. These symptoms happen because the UV damage is extensive enough to cause widespread inflammation and, in many cases, dehydration.
Confusion or disorientation is a particularly serious sign. If someone has a severe blistering sunburn and becomes confused, that’s a medical emergency. The American College of Emergency Physicians lists blistering sunburn combined with fever, chills, nausea, vomiting, or confusion as reasons to seek immediate care.
Medications That Make It More Likely
Some people develop sun poisoning far more easily than expected because of medications they’re taking. A surprising number of common drugs increase your skin’s sensitivity to UV light. These include certain antibiotics (particularly doxycycline and tetracycline), common pain relievers like ibuprofen and naproxen, cholesterol-lowering statins, blood pressure medications that contain diuretics, oral contraceptives, acne treatments containing retinoids, and even over-the-counter allergy medications.
Cosmetic products with alpha-hydroxy acids (AHAs) also thin the skin’s outer layer enough to make UV damage happen faster. The FDA maintains a full list of photosensitizing medications, and it’s longer than most people expect. If you burn unusually fast or severely despite using sunscreen, a medication you take daily could be the reason. Your pharmacist can tell you whether anything in your current prescriptions carries this risk.
How Sun Poisoning Heals
A regular sunburn peaks around day one or two and starts improving noticeably by day three. Sun poisoning follows a slower, more drawn-out timeline. The redness and swelling typically intensify for the first two to three days before stabilizing. Blisters may continue forming during this period, and once they begin to dry and flatten, the skin enters a prolonged peeling phase that can last a week or more.
During healing, the blistered skin is especially vulnerable to infection. Intact blisters should be left alone rather than popped, since the fluid inside acts as a natural bandage for the damaged tissue underneath. Cool compresses, staying well hydrated, and keeping the skin moisturized all help, but severe cases with widespread blistering or systemic symptoms like high fever often need professional treatment to manage pain and prevent complications.
PMLE follows a different pattern. The bumpy, itchy rash usually resolves on its own within a week or two once sun exposure stops. Over the course of summer, many people with PMLE find their skin gradually “hardens” to UV light, and the reaction becomes less severe with repeated, brief exposures. But the first outbreak of the season tends to be the worst.
How to Tell Which Type You Have
If your skin is deeply red, swollen, blistering, and painful after prolonged sun exposure, and you’re also running a fever or feeling nauseated, you’re dealing with a severe sunburn-type sun poisoning. The visual pattern follows the shape of your sun exposure: clear lines where clothing or sunscreen stopped, with the worst damage on the most directly exposed areas.
If your skin breaks out in clusters of small, itchy bumps or rough raised patches, especially on areas that rarely see sun, and you don’t feel systemically ill, PMLE is the more likely explanation. This tends to recur in the same pattern each time you get significant sun exposure.
Both warrant attention, but they call for different responses. Severe blistering sunburn with whole-body symptoms needs medical evaluation, particularly if blisters cover a large area or you develop confusion. PMLE is uncomfortable but usually self-limiting, though a dermatologist can confirm the diagnosis and suggest preventive strategies if it keeps recurring.