What's the largest organ of your body? Your skin, of course. The skin is more than a shell that covers our bones, tissues, and organs. It serves as a barrier against infection and injury, regulates our internal temperature, produces vitamin D, removes waste products from our body, shields us against the sun's radiation, and provides us with a sense of touch.

Our skin has 3 main layers, the epidermis, dermis, and subcutaneous fat tissue that protects our inner tissues from the harshness of the outside world (Fig. 1). The epidermis is the translucent (allows light to partially pass through it), thin, outside layer. The epidermis has 4 or 5 microscopic thin layers that do not contain blood vessels; it gets its oxygen and nutrients from the deeper layers of the skin. Underneath the epidermis lies the dermis, a thick layer composed of connective tissues containing nerves, lymphatic tissue, blood vessels, hair follicles, sweat glands, and sebaceous glands. Beneath the dermis is a layer of subcutaneous fat. The subcutaneous fat lies on our muscles and bones and attaches the skin structure using connective tissues.

Care for our skin should be one of our top priorities, but sadly it is often neglected. Many of us neglect our skin through unprotected sun exposure, putting us at risk for skin damage, immune system suppression, and even cancer.

Sun safety
We all need sun exposure; it's our primary source of vitamin D, which helps us absorb calcium for stronger, healthier bones. However, it doesn't take much time in the sun for most people to get all the vitamin D they need. After that, the risk of over-exposure can begin. Most children get between 50% and 80% of their lifetime sun exposure before age 18, so it's important for parents to teach their children how to safely enjoy fun in the sun.

Sunlight consists of 3 types of ultraviolet (UV) rays: UVA, UVB, and UVC (Fig. 2). UVA rays are most common and cause skin aging and wrinkling. Tanning beds usually use UVA and are not safer than the sun. UVB rays cause sunburns, cataracts, immune system damage, and contribute to skin cancer. UVC rays are the most dangerous; but fortunately, they are absorbed by our ozone layer; and therefore, can't harm us.

UV rays react with the pigment melanin in most people's skin. This pigment is your first defense against the sun. It absorbs dangerous UV rays before they do serious harm. The lighter your natural skin color, the less melanin you have to absorb UV rays. A sunburn develops when the amount of UV exposure is greater than what can be protected against by the skin's melanin. Both light- and dark-skinned individuals need protection against burning.

You should talk to your doctor or pharmacist about any medications you are taking that may increase your skin's sensitivity to UV rays. Many medications, prescribed and over-the-counter, increase sun sensitivity. Extra precautions are necessary in these situations.

Once burned
If you are sunburned, stay in the shade until the burn is healed. Take a cool bath to alleviate pain. Try pure aloe vera gel on the burn and take acetaminophen or ibuprofen for pain control. Apply topical moisturizer cream to rehydrate the skin and help reduce swelling.

What are the risk factors for skin cancer?
Risk factors for non-melanoma and melanoma skin cancers include the following:

• Unprotected or excessive exposure to ultraviolet (UV) radiation
• Fair complexion
• Occupational exposures to coal tar, pitch, creosote, arsenic compounds, or radium
• Family history
• Multiple or atypical moles
• Severe sunburns as a child

• Any change on the skin, especially in the size or color of a mole or other darkly pigmented growth or spot, or a new growth.
• Scaliness, oozing, bleeding, or change in the appearance of a bump or nodule.
• The spread of pigmentation beyond its border such as dark coloring that spreads past the edge of a mole or mark.
• A change in sensation, itchiness, tenderness, or pain.

• Seek the shade. Avoid the sun between 10 AM and 4 PM. Look for shade, especially in the middle of the day when the sun's rays are strongest. Practice the shadow rule and teach it to children. If your shadow is shorter than you, the sun's rays are at their strongest.
• Slip on a shirt. Cover up with protective clothing to guard as much skin as possible when you are out in the sun. Choose comfortable clothes made of tightly woven fabrics that you cannot see through when held up to a light.
• Slop on sunscreen. Use sunscreen with a sun protection factor (SPF) of 15 or higher. Apply a generous amount (about a palm full) and reapply after swimming, toweling dry, or perspiring. Use sunscreen even on hazy or overcast days.
• Slap on a hat. Cover your head with a wide-brimmed hat, shading your face, ears, and neck. If you choose a baseball cap, remember to protect your ears and neck with sunscreen.
• Slide on the shades. Wear sunglasses with 99 to100 percent UV absorption to provide optimal protection for the eyes and the surrounding skin.

Clark H. Cobb III, MD
Columbus, Georgia

Reference: American Academy of Family Physicians. familydoctor.org Web site. www.kidshealth.org. Sun Safety. 2004.