Consumer Health: Does expired sunscreen still work?

May is Skin Cancer Awareness Month, which makes this a good time to check the expiration date on last year's sunscreen.

It's that time of year when everyone's looking forward to some fun in the sun. Too much sun can be dangerous, though. Exposure to UV radiation from the sun damages your skin, and children are especially vulnerable because they tend to spend more time outdoors and can burn easily.

Skin damage from the sun increases your risk of developing:

• Skin cancer: Skin cancer develops primarily on areas of sun-exposed skin, including the scalp, face, lips, ears, neck, chest, arms, hands and legs. Skin cancer affects people of all skin tones, including those with darker complexions. Skin cancer occurs when mutations occur in the DNA of skin cells. Much of the damage to DNA in skin cells results from UV radiation found in sunlight and in the lights used in tanning beds.
• Wrinkles: Although genetics mainly determine skin structure and texture, sun exposure is a major cause of wrinkles, especially for people with light skin. Exposure to UV light breaks down your skin's connective tissue—collagen and elastin fibers, which lie in the deeper layer of skin. Without the supportive connective tissue, your skin loses strength and flexibility. Skin then begins to sag and wrinkle prematurely.
• Age spots: Age spots are caused by overactive pigment cells. UV light speeds up the production of melanin, a natural pigment that gives skin its color. On skin that has had years of sun exposure, age spots appear when melanin becomes clumped or is produced in high concentrations. Use of commercial tanning lamps and beds also can cause age spots.

One way to protect your skin is to use a broad-spectrum sunscreen with a sun protection factor, or SPF, of at least 30, even on cloudy days. Apply sunscreen generously, and reapply every two hours—or more often if you're swimming or perspiring. Use a generous amount of sunscreen on all exposed skin, including your lips, the tips of your ears, and the backs of your hands and neck.

Sunscreens are required by the Food and Drug Administration to remain at their original strength for at least three years. This means that you can use leftover sunscreen from one year to the next. Some sunscreens include an expiration date—a date indicating when they're no longer effective. Discard sunscreen that is past its expiration date. If you buy sunscreen that doesn't have an expiration date, write the date of purchase on the bottle. Throw out the bottle when three years have passed since the purchase date.

In addition to sunscreen, avoid sun exposure in the middle of the day when the UV rays are strongest, wear sunglasses that block both types of UV radiation—UVA and UVB rays—and wear a broad-brimmed hat and other protective clothing.

Exercising and enjoying time outdoors are important for good health. Staying protected from the sun will allow you and your family to do so safely.