Sun poisoning looks like an intense, deep-red sunburn that progresses to blisters, swelling, and sometimes oozing skin. Unlike a regular sunburn that fades to pink and peels, sun poisoning produces visible damage that goes beyond the skin’s surface layer, often accompanied by whole-body symptoms like fever, nausea, and chills.
The term “sun poisoning” isn’t a single medical diagnosis. It covers several distinct reactions to UV exposure, and each one looks different on the skin.
Severe Sunburn With Blisters
The most common form of sun poisoning is a second-degree sunburn. It starts as a bright red rash, but instead of just peeling over the next few days, it progresses to fluid-filled blisters. The skin appears moist and swollen, and it blanches white when you press on it. This happens because UV radiation has damaged not just the outermost layer of skin but the deeper tissue underneath, where blood vessels, oil glands, and hair follicles sit.
The blisters can range from small, scattered spots to large patches that merge together. In severe cases, the skin may look bright red and begin oozing clear or slightly yellowish fluid. The affected area is extremely painful to touch, often more so than a typical bad sunburn. On darker skin tones, the redness may be harder to see, but the blisters, swelling, and pain are still present. You may also notice that the skin feels hot and tight, almost drum-like.
Sun Allergy Rashes
Some people develop sun poisoning not from burn intensity but from an immune reaction to UV light. The most common version produces dense clusters of tiny bumps, raised rough patches, or small blisters on sun-exposed skin. This reaction can look different from person to person (which is why doctors call it “polymorphous,” meaning many forms), but itching and burning are almost always involved. The bumps tend to appear on the chest, arms, and lower legs rather than just the face and shoulders.
A less common reaction causes hives that appear within minutes of sun exposure. These look like flat red marks or raised red and white welts on the skin. One telltale sign: the welts often have sharp cutoff lines exactly where clothing covers the skin, creating a clear border between affected and protected areas. These hives typically fade within a few hours to a day and leave no scarring behind.
Whole-Body Symptoms That Set It Apart
What separates sun poisoning from a regular sunburn isn’t just the skin’s appearance. It’s the systemic symptoms that come with it. A normal sunburn stays on the surface. Sun poisoning makes you feel sick.
Fever and chills are common, sometimes starting several hours after exposure. Nausea and vomiting can follow, along with headache, dizziness, and general weakness. In serious cases, confusion or altered mental status can develop. These symptoms happen because the extensive skin damage triggers a widespread inflammatory response throughout your body, and because prolonged sun exposure also depletes fluids and electrolytes through sweating.
How It Differs From Heat-Related Illness
Sun poisoning and heat-related illnesses often happen at the same time, but they’re different problems. Heat exhaustion causes heavy sweating, headache, nausea, and weakness from losing too much water and salt. Your skin may feel clammy, but there’s no sunburn or blistering involved. Heat stroke is far more dangerous: the body loses its ability to cool itself, temperature can spike to 106°F or higher within 10 to 15 minutes, sweating may stop entirely, and confusion or loss of consciousness can follow.
The key distinction is the skin. Sun poisoning always involves visible skin damage (redness, blisters, swelling, or rash). Heat exhaustion and heat stroke can happen even if you’ve been in the shade, as long as it’s hot enough. That said, you can absolutely have both at once, which makes the combination more dangerous than either alone.
What the Progression Looks Like
Sun poisoning doesn’t peak the moment you come inside. The redness and pain typically intensify over the first 12 to 24 hours. Blisters may not appear until several hours after the initial burn, and swelling often continues to build overnight. The worst of it usually hits the day after exposure. Over the following days, blisters may break open and weep before crusting over. Full healing from a blistering sunburn can take one to two weeks depending on severity, and the skin underneath may remain pink and sensitive for longer.
For sun allergy reactions, the timeline is different. Hives from solar urticaria appear within minutes and usually resolve within hours. The bumpy, itchy rash from a polymorphous light eruption may take a day or two to fully develop and can linger for a week or more if you keep getting sun exposure.
Signs That Need Immediate Attention
Certain combinations of symptoms signal that sun poisoning has become a medical emergency. Blisters covering a large area of your body, especially paired with fever, chills, nausea, vomiting, or confusion, require prompt care. Bright red skin that’s actively oozing is another red flag. If someone who’s been in the sun develops confusion, slurred speech, or stops sweating despite being in the heat, that points to heat stroke, which can become life-threatening within minutes.
Small, localized blisters from a sunburn on one body part, while painful, can often be managed at home with cool compresses, hydration, and over-the-counter pain relief. But when the damage is widespread or your body is reacting systemically with fever and nausea, the situation has moved beyond what a cold shower and aloe can handle.