Sunburn: what the burn is doing to your skin and how to treat it
Last updated September 3, 2026.
Sunburn is a radiation burn from UV light, and the redness you see is your skin's emergency repair response in action. The damage peaks 12-24 hours after exposure, which is why a burn often looks worse the next morning. Most sunburn heals in about a week with simple care; the serious part is what repeated burns do over years: skin aging and a raised skin cancer risk, especially with blistering burns in childhood.
What does it do, hour by hour?
The burn develops slowly: skin turns pink then red over the first hours, hot and tender to touch, peaking around 24 hours. Mild burns settle in 3-5 days with peeling, which is the body shedding the damaged layer. Moderate burns blister: fluid-filled bubbles that are nature's sterile dressing. The red-flag symptoms are systemic: fever, chills, dizziness, nausea, headache, and dehydration, which signal sun poisoning territory (a severe burn reaction) or overlapping heat illness. Sunburned skin tans then peels; the tan is damage, not health, and it offers almost no protection against the next burn (about SPF 3).
How do you treat it?
Get out of the sun the moment you notice pinkness; the burn keeps developing. Cool the skin: cool showers, damp towels, or a soak, 10-15 minutes several times a day, then moisturize while damp with plain aloe vera or a simple fragrance-free moisturizer. Ibuprofen early (in the first day) genuinely reduces the inflammation and pain. Drink extra water; a burn pulls fluid to the skin surface. Leave blisters alone: unpopped they prevent infection. Do not put butter, toothpaste, or petroleum-heavy products on a fresh burn, and skip products ending in -caine, which irritate and can trigger allergy.
What actually helps?
- Cool, then moisturize: cool compresses or showers, then aloe vera or plain moisturizer on damp skin, repeated through the day.
- Ibuprofen early: started within the first 24 hours, it measurably reduces redness and pain; acetaminophen works for pain alone.
- Hydrate: burns draw fluid; headache and dizziness on a burn day are often dehydration.
- Do not pop blisters: if one breaks, gently clean it, apply a plain moisturizer or petroleum jelly, and cover with a loose non-stick dressing.
- Protect healing skin: new skin burns fast; cover up and use high SPF on it for weeks, not days.
When is it an emergency?
Most sunburn is home care. Escalate for: blistering over a large area, especially in a child; fever over 38.5C (101.3F) with the burn; severe pain uncontrolled by painkillers; signs of heat illness (confusion, fainting, no sweating in the heat, racing pulse), which is an emergency; signs of infection in broken blisters (spreading redness, pus, red streaks); and any burn in a baby under 1 year, which always gets medical advice. Eye pain from UV (welder's-flash style) is a separate same-day issue. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
How long does sunburn last?
The typical arc: redness and heat build over 24 hours, the worst pain is days 1-2, peeling starts around day 3-5, and the burn resolves in about a week for mild-to-moderate cases. Blistered burns take longer, 2 weeks or more. The peel is non-negotiable healing, not damage to fight: let skin shed itself, and keep moisturizing. Pigment changes (darker or lighter patches) can linger for months after a bad burn before evening out.
Is sunburn with blisters serious?
Blistering means a second-degree burn: deeper damage than simple redness. It is still usually home-treatable, but the rules tighten: never pop the blisters (they are sterile dressings and infection is the risk), cover broken ones loosely, and expect a couple of weeks of healing. Large-area blistering, blistering on a baby or toddler, or blistering with fever and chills moves it into get-medical-advice territory. Blistering sunburns, especially in childhood, are the burns most strongly linked to later skin cancer risk, so they are also a permanent sunscreen reminder.
Does a tan protect me from burning?
Barely. A tan offers roughly SPF 3, which is close to nothing, and the tan itself is visible evidence of DNA damage already done: tanning is the skin's injury response, not armor. People who tan well burn too, just later into the exposure. The darker your natural skin tone, the more built-in protection you have, but UV damage, burns, and skin cancer happen in every skin tone, and darker skin often shows sun damage as uneven pigmentation rather than redness.
What SPF should I actually use, and how much?
SPF 30 minimum, broad spectrum (UVA and UVB), and the amount is where everyone fails: about 2mg per square centimeter of skin, which works out to a shot-glass (roughly 30ml) for a full body in a swimsuit, and a teaspoon for face and neck. Most people apply a quarter to a half of that and get a fraction of the labeled protection. Reapply every 2 hours and after swimming, sweating, or toweling. Water-resistant means 40-80 minutes in water, not all day.
Is it safe to put vinegar, butter, or toothpaste on a sunburn?
No to the kitchen remedies. Butter and oils trap heat in a fresh burn. Toothpaste irritates and does nothing. Vinegar is folk tradition without evidence and can sting broken skin. The products that actually help: cool water, plain aloe vera gel, simple fragrance-free moisturizer, and ibuprofen by mouth. Also skip topical anesthetics ending in -caine (benzocaine, lidocaine sprays) on sunburn: they irritate healing skin and cause allergic reactions in some people.
Can you get sunburned through clouds or windows?
Clouds, yes: up to 80-90% of UV passes through light cloud, and bright overcast days cause many of the worst burns because nobody reapplies. Windows, mostly no: ordinary glass blocks UVB (the burning rays) but lets UVA (the aging, deeper-damaging rays) through, which is why drivers and desk-by-window workers accumulate one-sided damage over years. Water, sand, and snow all reflect UV upward, roughly doubling effective exposure, which is why shade alone at the beach does not prevent a burn.