Test Your Knowledge

Excessive sun exposure over time can be harmful to the skin because the sun emits an invisible form of radiation called ultraviolet (UV) radiation. The UV rays present in sunlight can penetrate the skin and alter the structure of its cells. The ultraviolet radiation received from sun exposure is also present in the light exposure received from sun lamps and tanning beds.

The three types of UV radiation include:

• Ultraviolet A (UVA). The most abundant source of solar radiation at the surface of the earth, UVA rays can penetrate beyond the surface of the skin (epidermis) to the middle layer of skin (dermis).
  
  

  

• Ultraviolet B (UVB). These rays are less plentiful at the earth’s surface than UVA rays because the ozone layer (the protective layer in the earth’s atmosphere) absorbs a large portion of UVB rays. UVB rays penetrate only the epidermal skin layer. However, they are the most harmful form of ultraviolet radiation.
  
  
• Ultraviolet C (UVC). Although these solar rays would be especially harmful to the skin, they are completely absorbed by the ozone layer and never reach the earth’s surface.

UV rays are not only present on bright, sunny days. They are emitted on cloudy and hazy days as well. In addition, UV rays reflect off surfaces such as water, sand, concrete and snow.

When UV rays penetrate the epidermis, their energy interacts with cells called melanocytes to produce a colored substance called melanin. Melanin produces the darker coloring of skin. The new melanin eventually travels toward the surface of the skin to protect it from UV rays and the skin becomes darker, or tans. Some physicians believe that tanning is the skin’s response to injury because it occurs after UV rays from the sun have damaged and killed some skin cells.

Eventually, the UV rays will cause the skin to burn. Sunburn is often accompanied by redness, swelling and pain in the affected region(s). If the sunburn is particularly severe, the damaged skin may peel away and be replaced by new skin cells. Although sunburn symptoms diminish over time, the resulting skin damage will remain. Severe sunburn can even alter some of the genetic structure of skin cells. This may lead them to create new cells that are damaged, which may eventually lead to skin cancer.

Some individuals tan very easily and rarely burn, whereas others burn with minimal sun exposure and rarely tan. Numerous factors determine whether a person tans or burns after sun exposure. These include skin type, amount of recent sun exposure, time of year and sun strength. The American Academy of Dermatology (AAD) and the U. S. Food and Drug Administration (FDA) use a six-level scale to classify an individual’s susceptibility to sunburn:

Brief, unprotected sun exposure (10 to 15 minutes on the face, hands, arms or back twice a week) can be beneficial because it helps the body produce vitamin D. This nutrient is essential for the maintenance of healthy bones and teeth. However, the AAD urges people to practice sun protection and seek vitamin D through diet instead. Vitamin D can be found in many foods, including fortified milk and breakfast cereals, eggs, mushrooms, herring and salmon.

Although everyone is at risk for sun damage, the following factors increase an individual’s likelihood of sustaining damage, particularly skin cancer:

• Fair skin
• Light-colored eyes
• Light-colored hair
• Lack of sunscreen protection
• Having had one or more serious sunburns
• Many moles, birthmarks or freckles
• Playing or working outdoors
• Frequent sun exposure during childhood
• Personal or family history of skin cancer
• Frequent tanning or use of sun lamps or tanning beds
• Living in a tropical or subtropical climate
• Living at high altitudes

Taking certain medications, including specific forms of antibiotics, nonsteroidal anti-inflammatory drugs, tricyclic antidepressants, diuretics, sulfonylureas and immunosuppressants, can also increase the risk of sun damage by increasing photosensitivity (sun sensitivity) and burning.

It is recommended that individuals have regular physical examinations by a dermatologist to detect or determine the risk of skin cancer and other damage.