A sunburn is an inflammation or blistering of the skin caused by overexposure to the sun.
Sunburn is caused by excessive exposure to the ultraviolet (UV) rays of the sun. There are two types of ultraviolet rays, UVA and UVB. UVA rays penetrate the skin deeply and can cause melanoma in susceptible people. UVB rays, which don't penetrate as deeply, cause sunburn and wrinkling. Most UVB rays are absorbed by sunscreens, but only about half the UVA rays are absorbed.
Skin cancer from sun overexposure is a serious health problem in the United States, affecting almost one million Americans each year. One person out of 87 will develop malignant melanoma, the most serious type of skin cancer, and 7,300 of them will die each year. The Environmental Protection Agency (EPA) reported in 2000 that the rate of malignant melanoma is rising faster in the United States than the rates of all other preventable cancers except lung cancer. One reason for this high rate is the popular belief that suntanned skin is healthy and attractive. Many people spend more time in the sun than is good for their skin trying to achieve a fashionable tan.
People with fair skin are most susceptible to sunburn, because their skin produces only small amounts of the protective black or dark brown pigment called melanin. However, people of any race can get sunburned if they do not protect their skin against overexposure. People trying to get a tan too quickly in strong sunlight are also more vulnerable to sunburn.
Causes & symptoms
The ultraviolet rays in sunlight destroy cells in the outer layer of the skin, damaging tiny blood vessels underneath. When the skin is burned, the blood vessels dilate and leak fluid. Cells stop making protein. Their DNA is damaged by the ultraviolet rays. Repeated DNA damage can lead to cancer.
When the sun burns the skin, it triggers immune defenses which identify the burned skin as foreign. At the same time, the sun transforms a substance on the skin which interferes with this immune response. While this substance keeps the immune system from attacking a person's own skin, it also means that any malignant cells in the skin will be able to grow freely.
Sunburn causes skin to turn red and blister. Several days later, the dead skin cells peel off. In severe cases, the burn may occur with sunstroke (vomiting, fever, and fainting).
While overexposure to the sun is harmful, even fatal, no exposure means the body can't manufacture vitamin D, which is the only vitamin whose biologically active form is a hormone. Vitamin D is produced in the skin from the energy of the sun's UV rays. People at risk for vitamin D deficiency include alcoholics, non-milk drinkers, and those who do not receive much sunlight—especially those who live in regions that get little natural light. Dr. Sheldon Saul Hendles says that as more people use sunscreens and decrease exposure to the sun, they should make sure to have adequate dietary and supplementary sources of vitamin D. Sunscreen prevents the synthesis of the vitamin.
Symptoms of sunburn may not appear until several hours after exposure. A deep pink skin color accompanied by a sensation of heat and burning indicates a mild sunburn. A red color with visible clothing lines, burning, itching, and stinging indicates a moderate burn. Bright red skin with blisters, fever, chills, and nausea indicates severe burn and medical help should be sought quickly.
Over-the-counter preparations containing aloe (Aloe barbadensis) are an effective treatment for sunburn, easing
Other natural remedies include:
- Applying compresses dipped in cold water, one part skim milk mixed with four parts cold water, aluminum acetate antiseptic powder mixed with water, witch hazel, white vinegar, or baking soda mixed with water.
- Making a paste out of cornstarch and water, and applying directed to affected areas.
- Placing thin, cold slices of raw cucumber, potato, or apple on the burned areas.
- Making a soothing solution by boiling lettuce in water, strain, cool the water for several hours in the refrigerator, then use cotton balls to pat the liquid onto the skin.
- Applying tea bags soaked in cold water to burned eyelids.
- Soothing the burn with cool yogurt, then rinsing with a cold shower.
Another natural remedy that has been proposed for treating sunburn is gingko biloba extract. A Turkish study published in 2002 reported that gingko biloba appears to heal sunburned skin after exposure as well as protect against ultraviolet radiation before exposure. These findings, however, await confirmation by other researchers.
Aspirin can ease pain and inflammation. Tender skin should be protected against the sun until it has healed.
In addition, people suffering from sunburn may apply:
- calamine lotion
- sunburn cream or spray
- cool tap-water compresses
- colloidal oatmeal (Aveeno) baths
- dusting powder to reduce chafing
People who are severely sunburned should see a doctor, who may prescribe corticosteroid cream to speed healing and prescription pain medication. Topical corticosteroids that have been shown to be safe as well as effective in treating sunburn include methylprednisolone aceponate and hydrocortisone 17-butyrate.
Moderately burned skin should heal within a week. While the skin will heal after a sunburn, the risk of skin
Sun protection education
Concern about the rising rate of melanoma in Europe, Australia, and the United States has led public health experts to recommend adding instruction about the importance of sun protection to elementary and junior high school programs. A 1999 cross-sectional study of boys and girls in all 50 states found that 83% of the students had at least one sunburn during the previous summer, with 36% reporting three or more episodes of sunburn. Only 34% used sunscreen. As of 1998, only 3.4% of schools in the United States had sun protection policies to protect students from excessive sun exposure during recess or athletic practice. A standardized program of sun protection education developed by the EPA in 2000 has been reported to be effective in changing students' attitudes toward tanning and the importance of using sunscreen.
Specific preventive measures
To prevent sunburn, everyone over the age of six months should use a water-resistant sunscreen with a sun protective factor (SPF) of at least 15. Apply at least an ounce of sunscreen 15–30 minutes before going outside. It should be reapplied every two hours (more often after swimming). Babies should be kept completely out of the sun for the first six months of life, because their skin is thinner than the skin of older children. Sunscreens have not been approved for infants. Some people are allergic to para-aminobenzoic acid (PABA), a major ingredient in sunscreen products. They should check all labels or consult a doctor prior to application.
In addition, people should follow these guidelines:
- Limit sun exposure to 15 minutes the first day, even if the weather is hazy; then slowly increase exposure daily.
- Reapply sunscreen every two hours (more often if swimming or perspiring heavily).
- Reapply waterproof sunscreen after swimming more than 80 minutes, after toweling off, or after perspiring heavily.
- Avoid exposure to the sun between 10 A.M. and 3 P.M.
- Use waterproof sunscreen on legs and feet, since sun rays can burn even through water.
- Wear an opaque shirt in water, because reflected rays are intensified.
Patients using a sunscreen rated lower than SPF 15 should note that simply applying more of the same SPF won't prolong allowed time in the sun. Instead, patients should use a higher SPF in order to safely lengthen their exposure time. A billed cap protects 70% of the face; a wide-brimmed hat is better. People at very high risk for skin cancer can wear clothing that blocks almost all UV rays, but most people can simply wear white cotton summer-weight clothing with a tight weave. As of 2001, the U.S. Food and Drug Administration requires all sunscreen makers to label their products as providing minimum, moderate, or high levels of sun protection.
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American Academy of Dermatology. 930 East Woodfield Rd., PO Box 4014, Schaumburg, IL 60168. (847) 330-0230. <www.aad.org>.
Environmental Protection Agency. Ten regional offices with region-specific addresses and phone numbers. <www.epa.gov>.
Ken R. Wells
Rebecca J. Frey, PhD