Sunburn is the term for red, sometimes swollen, and painful skin caused by overexposure to ultraviolet (UV) rays from the sun. Sunburn can vary from mild to severe.

The extent depends on skin type and amount of exposure to the sun. Sunburn is a serious risk factor for skin cancer.

Because of variations in the intensity of UV radiation passing through the atmosphere, the risk of sunburn increases as you approach the equator. The higher the latitude, the lower the intensity of the UV rays.

On a minute-by-minute basis, the amount of UV radiation is dependent on the angle of the sun. The greatest risk is at solar noon when the sun is directly above you.

Fast facts on sunburn

Here are some key points about sunburn. More detail and supporting information is in the main article.

  • Sunburn is caused by ultraviolet light from the sun.
  • In some cases, sunburn can cause the skin to blister.
  • Sunburn can be soothed by home remedies.
  • Avoiding sunburn in the first place is better than having to treat its effects.

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Sunburn can be very uncomfortable indeed.

The symptoms of sunburn vary from person to person. You may not notice redness of the skin for several hours after the burn has begun. Peak redness will take 12-24 hours.

Minor sunburns typically cause nothing more than slight redness and tenderness to the affected areas.

In more serious cases, blistering can occur. Extreme sunburns can be painful to the point of debilitation and may require hospital care.

In much more severe cases, symptoms include:

  • fever
  • chills
  • nausea and vomiting
  • weakness

In extreme cases, symptoms of shock can occur, for instance:

Sunburn can occur in less than 15 minutes, but the harm is often not immediately obvious.

After the exposure, skin may turn red in as little as 30 minutes, but most often takes 2-6 hours. Pain is usually most extreme 6-48 hours after exposure. The burn continues to develop for 24-72 hours, sometimes followed by peeling skin in 3-8 days.

Some peeling and itching may continue for several weeks.

It is important to start treatment for sunburn as soon as possible. Sunburn can lead to permanent skin damage and increase the risk of skin cancer. The following are some simple ways to ease the discomfort of sunburn; however, it important to bear in mind that the best way to relieve suffering is to avoid being sunburned in the first place:

Pain relief - over-the-counter (OTC) pain relief such as ibuprofen or other nonsteroidal anti-inflammatory medications (NSAIDs) can help relieve the pain and reduce swelling. It is best to take these as soon as possible. Some pain relief can be applied as a topical ointment.

Hydrocortisone cream - may also help reduce inflammation and itching.

Rehydrate - drink water to help rehydrate the skin.

Don't break small blisters - allow them to run their course. If one breaks, clean it with mild soap and water.

Peeling skin - do not pick, and continue to apply moisturizer.

Cool the skin - apply a damp cloth or towel, or take a cool bath.

Do not use butter - this is a false remedy that can prevent healing and damage skin.

Apply moisturizer - for instance, aloe vera gel.

Stay out of the sun - avoid making the burn worse by exposing it to more UV.

If the sunburn is severe enough, oral steroid therapy (cortisone-like medications) may be prescribed for several days. However, steroid creams placed on the skin show minimal to no benefit.

If blistering is present, steroids may be withheld to avoid an increased risk of infection. If the patient is dehydrated or suffering from heat stress, IV (intravenous) fluids will be given.

A mild sunburn does not normally require a visit to the doctor. However, if there are severe symptoms, it is important to seek medical attention.

A doctor will ask about symptoms and medical history. A physical exam will be conducted and, for more severe cases of sun damage, a person may be referred to a doctor who specializes in skin disorders or a dermatologist.

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There is a range of ways to avoid sunburn.

The best way to avoid sunburn is to minimize the amount of time skin is exposed to sunlight:

  • sit in locations with shade
  • wear a wide-brimmed hat
  • protect the eyes with sunglasses
  • avoid going out in the hottest part of the day
  • always wear sunblock and reapply regularly

How to choose sunblock

Commercial preparations are available that block UV light, known as sunscreens or sunblocks. They have a sunburn protection factor (SPF) rating, based on the sunblock's ability to suppress sunburn. Basically, the higher the SPF rating, the lower the amount of direct skin damage.

A sunscreen rated as SPF 10 blocks 90 percent of the sunburn-causing UVB radiation; an SPF20 rated sunscreen blocks 95 percent.

Modern sunscreens contain filters for UVA radiation as well as UVB. Although UVA radiation does not cause sunburn, it does contribute to skin aging and an increased risk of skin cancer. Many sunscreens provide broad-spectrum protection, meaning that they protect against both UVA and UVB radiation.

Research has shown that the best protection is achieved by application 15-30 minutes before exposure, followed by one reapplication 15-30 minutes after exposure begins.