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  • Writer's pictureAlan Frischer, MD, MPH


Plentiful sunshine brings with it outdoor activities, and increased exposure to the harmful effects of the sun. What impact does that have on our health?

In addition to giving off heat and light, the sun emits three types of ultraviolet (UV) rays. UVA rays are the most common form of sun exposure. UVB rays are less common but more intense. UVC rays are the most dangerous, but fortunately Earth’s ozone layer blocks them.

We don’t see UV rays, but they penetrate our skin. A little anatomy is helpful: The inner layer of our skin is the dermis, where the nerves and blood vessels are. The outer layer of our skin is the epidermis, which contains the pigment melanin. Melanin protects our skin and helps to make vitamin D. Those of us with lighter complexions have less melanin than darker-skinned people, and this is why fair-skinned people burn more easily.

When our body defends itself against UV rays, the skin darkens, or tans. Too much sun exposure allows UV rays to reach the inner skin layers. This is sunburn, and causes redness, skin that is warmer to the touch, pain, itching, blisters, dehydration and peeling. It can cause skin cells to die, to be damaged, or to develop cancer.

Note that some sun exposure is important:

  • A small amount of exposure to UV rays produces vitamin D, which helps the body to absorb calcium. Calcium is necessary to build and maintain healthy bones. (Vitamin D is also effective when we get it from various foods and supplements.)

  • UV rays are useful for the treatment of conditions like eczema, psoriasis, rickets, and jaundice.

However, UV rays can certainly be harmful:

  • Excess exposure leads to skin changes that result in freckles, moles, and skin cancers.

  • UV rays can lead to early aging of the skin, which includes wrinkles, tight skin, leathery skin, and dark spots.

  • Too much sun exposure can lead to a weakened immune system. When the skin burns, existing white blood cells are used to repair the damage, pulling them away from other immune system tasks.

  • UV rays can burn the cornea, or outer layer, of our eyes. Over time, cataracts may develop, leading to blindness if untreated.

  • Extended exposure to UV light increases the risk of developing macular degeneration, which is the leading cause of age-related blindness.

Remember, we are all at risk from the effects of sun exposure. It doesn’t matter how old we are or what our skin color is. Those who work or play outdoors need plenty of extra protection. So, enjoy our wonderful Southern California summer, and exercise caution with proper hats, sunglasses, clothing, sunscreen, and limited exposure.

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