A bad sunburn goes beyond simple redness. It can range from deep, angry red skin that’s hot to the touch all the way to blistered, swollen, oozing skin that signals a second-degree burn. The severity depends on how deep the UV damage reaches, and what you see on the surface tells you a lot about what’s happening underneath.
Mild vs. Severe: How to Tell the Difference
A mild sunburn affects only the outermost layer of skin. It looks red, feels hot, and is dry to the touch. There are no blisters, no swelling, and no broken skin. It hurts, but the skin stays intact. This is a first-degree burn.
A bad sunburn crosses into second-degree territory. The clearest visual sign is blisters: raised pockets of skin filled with clear, watery fluid called serum. Small blisters (under half an inch) are common, but severe burns can produce larger ones. The surrounding skin may look bright red, swollen, and wet or shiny from fluid that oozes out. In the worst cases, the top layer of skin begins to slough off on its own, exposing raw, tender skin underneath.
Deep second-degree sunburns look different from what most people expect. Instead of bright red, the skin can turn white, gray, yellow, or a mottled mix of these colors. This discoloration means the damage has reached deeper layers of skin. The burned area may still blister, but the skin also sheds in sheets rather than the typical light peeling you’d see a few days after a mild burn.
How a Bad Sunburn Develops Over Time
Sunburn doesn’t show its full severity right away. Pain typically starts within a few hours of exposure, but the redness and irritation keep intensifying. Your skin will look significantly worse at the 24-hour mark, when redness, swelling, and pain all peak. This means a sunburn that looks moderate in the evening could look alarming by the next morning.
Blisters usually appear within the first 6 to 24 hours. If your skin is going to blister, you’ll likely notice the first ones forming overnight or the next day. Over the following days to a week, the pain fades and the skin begins to peel as damaged cells are shed and replaced. A mild sunburn resolves within a few days. A blistering sunburn takes longer and carries a higher risk of complications.
Whole-Body Symptoms That Signal Trouble
A truly bad sunburn doesn’t just affect your skin. When the burn is severe enough, your body mounts a systemic response sometimes called “sun poisoning.” This isn’t actually poisoning, but the symptoms can feel like it. You may experience fever, chills, or find yourself shivering despite warm surroundings. Headache, nausea, and vomiting are common. Some people feel dizzy, lightheaded, confused, or even faint.
Much of this comes from dehydration. Severe sunburns pull fluid and electrolytes out of your bloodstream and into the damaged skin, which is why blistering burns ooze so much. If you’re experiencing extreme thirst, nausea, dizziness, or general illness alongside a bad sunburn, dehydration is the likely driver. Drinking fluids aggressively helps, but these symptoms alongside blistering skin warrant medical attention.
What Infected Sunburn Looks Like
As a bad sunburn heals, it’s normal for skin to peel, feel tight, and look patchy. What’s not normal is skin that gets worse after the first few days instead of better. Signs of infection include increasing redness that spreads beyond the original burn area, red streaks radiating outward from blisters, pus or yellow-green drainage (as opposed to the clear fluid of a normal blister), warmth that intensifies rather than fading, and worsening pain after the initial peak.
Blisters create openings in the skin barrier, which is why popping them increases infection risk. Intact blisters, even large ones, are your body’s natural wound dressing. If a blister breaks on its own, keeping the area clean and covered matters.
When a Sunburn Needs Medical Care
Not every bad sunburn requires a trip to urgent care, but certain combinations of symptoms do. Blistering over a large area of your body is one of the clearest triggers. Federal burn treatment guidelines flag second-degree burns covering more than 20% of the body’s surface area in adults as needing specialized care. For children under 10 and adults over 50, that threshold drops to 10%.
Location matters too. Second-degree sunburns on the face, hands, feet, or over major joints like elbows and knees are treated more seriously because of the risk of scarring and restricted movement during healing.
The combination of blistering skin with systemic symptoms, specifically bright red oozing skin alongside fever, severe pain, shivering, nausea, or vomiting, is the clearest signal to get professional help. The same goes for any sunburn where you feel confused, short of breath, or close to fainting, as these suggest significant dehydration or heat illness on top of the burn itself.