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Facts About Sunscreen

Summertime brings plenty of chances for fun in the sun. The use of sunscreens can help avoid overexposure to sunlight. Ultraviolet light is the portion of sunlight which causes both tans and burns. This range of light is divided into three classifications: UV-A, -B, and -C. UV-A causes skin to tan, UV-B causes skin to burn, and UV-C is absorbed in the ozone layer and does not reach earth.


As we are exposed to sunlight, UV-A causes the melanin in the skin to oxidize resulting in a tan. New melanin forms and the tan darkens to protect the skin from damage by UV-B. UV-B causes sunburns which may range from slight redness to painful blisters. Long term exposure to UV-B can lead to increased skin thickness, wrinkles, and precancerous conditions which can further lead to carcinomas and malignant melanomas. UV-A may also contribute to the development of skin cancer.

Many dermatologists advocate the use of sunscreens which prevent absorption of the harmful UV rays. Each product is given a sun protection factor (SPF) to indicate its blocking ability. A low SPF indicates a low level of blocking while a higher SPF allows for more protection.


Sunscreens are further classified into two groups: chemical and physical. Chemical sunscreens include para-aminobenzoic acid (PABA), padimate, oxybenzone, salicylate salts and others. These agents work by absorbing specific wavelengths of UV light and reduce their penetration through the skin. Physical agents, such as zinc oxide and titanium dioxide, work by scattering the UV rays to prevent absorption.


Sunscreens have a low incidence of side effects, but some people experience burning, stinging, and/or redness with use of these products. Individuals can be sensitive to the oils, fragrances, alcohols, and/or dyes (such as tartrazine) that these products may contain. Accidental ingestion of sunscreen may cause mild stomach upset and diarrhea. Little information is available regarding the safety of chronic sunscreen usage, but commercially available sunscreens appear to have a low incidence of adverse effects.

Ingestions of either chemical or physical sunblock should not be a problem unless very large amounts are consumed or if the patient is allergic to any of the ingredients. If irritation develops after skin application, wash it off and discontinue further use. Eye exposures may be very irritating but are unlikely to be corrosive or cause severe damage.


Sunscreens should be applied to all exposed areas including the lips. They should only be used in children under six months of age if directed by a physician. In order to be effective, sunscreens need to be applied before exposure and reapplied every 1-2 hours, especially following swimming or excessive sweating. Remember to check the expiration date on the product. In general, sunscreens are effective for 3 years, however manufacturers also place an expiration date on the bottle. Sunscreen should not be used past the expiration date since it may no longer be effective.

Summer is a time for fun and sun, but also a time to be careful. Enjoy those days by the pool or in the park, but be sun smart!

If you have any questions about sunscreen, call the Missouri Poison Center at 1-800-222-1222. The poison center is open all day, every day for poisoning emergencies and questions.

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