A mild sunburn is at its worst 12 to 24 hours after exposure and fades over three to five days. A more serious one — deep red, tight, tender to touch — runs about a week, usually with peeling. A blistering sunburn is a second-degree burn and can take two weeks or more, sometimes leaving discolouration for months.
Here is the full timeline, what shortens it, what does not, and the point at which a sunburn stops being something to manage at home.
The timeline
Hours 0–2: nothing visible. This is the cruel part. The ultraviolet damage happens while you are in the sun, but the inflammatory response that makes it visible takes hours to develop. You cannot judge exposure by how your skin looks at the time — by the time you can see it, you took the dose hours ago.
Hours 2–6: redness appears. Blood vessels dilate in response to inflammatory mediators. Skin begins to feel warm and tight.
Hours 12–24: peak. Redness, heat, tenderness and swelling are at maximum. If blisters are going to form, they usually appear in this window. This is when the burn is genuinely painful.
Days 2–3: the plateau. Pain begins to subside; redness starts to shift toward brown or, in fair skin, stays pink. Itching often starts here.
Days 3–8: peeling. The damaged outer layer is shed. Peeling is a sign the burn was significant enough to kill epidermal cells — it is not a sign of healing gone wrong, and it is not something to accelerate.
Weeks 1–4: discolouration. Uneven pigmentation, especially after a burn that peeled, can persist for weeks. Deeper skin tones may see post-inflammatory hyperpigmentation lasting considerably longer.
How severity changes the clock
| Severity | Signs | Typical duration |
|---|---|---|
| Mild (first degree) | Pink, warm, mildly tender; no blisters | 3–5 days, little or no peeling |
| Moderate (first degree) | Bright red, tight, painful; swelling | 5–7 days, peeling around day 4–7 |
| Severe (superficial second degree) | Deep red, blistering, significant pain | 1–2 weeks; risk of scarring and infection |
| With heat illness | Any of the above plus fever, chills, nausea, dizziness, headache | Needs medical assessment, not a timeline |
Duration also depends on where the burn is. Skin turns over faster on the face than on the back or shins, so facial burns generally clear a couple of days sooner. Age, hydration and overall skin condition shift it as well.
What actually helps
Cool it down. Cool (not cold) showers or cool damp compresses for 10–15 minutes at a time reduce heat and pain. Avoid ice directly on the skin — it can worsen the injury.
Moisturise while damp. Apply a plain, fragrance-free moisturiser or an aloe vera gel while the skin is still slightly wet. This traps water in the skin, which is the main thing that eases tightness and reduces peeling.
Anti-inflammatories. An over-the-counter NSAID such as ibuprofen, taken as directed on the packet, addresses the inflammation directly and helps with pain, particularly in the first 24 hours. Follow the label and any advice specific to your medical history.
Drink. Burned skin loses fluid into the tissue. Increase fluid intake for the first day or two.
Cover up completely until it has healed. Re-exposing burned skin stacks damage on damage and extends the whole timeline.
Leave blisters alone. Intact blisters are a sterile dressing. If one bursts on its own, clean the area gently and cover it loosely.
What does not help — and what makes it worse
- Petroleum jelly or thick oils on a fresh burn. They trap heat in the skin.
- Benzocaine or lidocaine "sunburn sprays". They can provoke contact allergy on already-damaged skin.
- Butter, toothpaste, vinegar, and other kitchen remedies. No evidence of benefit; some carry a genuine infection risk.
- Peeling the skin off deliberately. It removes a layer that is still protecting the tissue underneath and increases scarring risk.
- Exfoliants, retinoids or acids. Pause them entirely until the skin has fully recovered.
- Hot showers and swimming pools. Heat and chlorine both aggravate it.
- "Working through it" with more sun. A burn on top of a burn is what turns a five-day problem into a fortnight.
Nothing you can apply afterwards will undo the DNA damage that was done during the exposure. Aftercare manages symptoms and supports healing; it does not reverse the injury.
When to seek medical help
See a doctor promptly if any of these apply:
- Blistering over a large area — roughly more than the surface of one arm, or blistering on the face, hands, feet or genitals.
- Fever, chills, nausea, vomiting, headache, confusion, rapid pulse or fainting. Often called "sun poisoning", this is systemic illness — heat exhaustion or a severe burn reaction — not just skin damage.
- Signs of infection: increasing pain after day two, spreading redness, warmth beyond the burn edge, yellow discharge, or red streaks.
- Severe pain that over-the-counter analgesia does not touch.
- A sunburn in an infant under one year old — always worth medical assessment.
- Any burn while taking photosensitising medication, or with a condition such as lupus.
The part that does not fade
The redness resolves. The DNA damage that caused it is repaired imperfectly, and a fraction persists as mutations in surviving cells. Epidemiological studies link intermittent, intense exposure — the pattern that produces sunburn — to melanoma risk more strongly than they link steady occupational exposure, and the association is dose-dependent: the more burns, particularly in childhood and adolescence, the higher the risk.
That is the real reason to care about the timeline. A week of discomfort is the visible cost; it is not the whole cost.
Not getting the next one
Sunburn is almost always a timing error rather than a judgement error. People misjudge how quickly the UV index rises toward solar noon, and because the redness takes hours to appear, there is no feedback while it matters.
That gap is what Sunlit closes: it reads the live UV index for your location, works out how long your skin type can actually stay out at that intensity given your SPF, and runs the exposure as a timer with turn-over and reapplication alerts — so the decision is made before you are out there rather than the following morning. Free on iPhone and iPad.
Related reading
- Sun Poisoning Symptoms: When a Sunburn Needs a Doctor
- How to Tan Without Burning: A Step-by-Step Method
- Can You Tan With Sunscreen On? Yes — Here's Why
This article is general information, not medical advice, and does not replace assessment by a healthcare professional. If you are unsure how serious a burn is, or if any of the warning signs above are present, seek medical care. Sources: American Academy of Dermatology public guidance on sunburn treatment; NHS guidance on sunburn; IARC Monographs Vol. 100D on solar radiation; published reviews of erythema onset and resolution timing.
