The sun produces three kinds of ultraviolet radiation: UVA, UVB and UVC. The types of UV rays are categorized by their different wavelengths. UVC rays have the shortest wavelength, so they are usually absorbed by the ozone layer and rarely make it to Earth. UVA and UVB rays do make it to the earth’s surface, however, and both can have a profound impact on your skin.

To know how they each affect the skin, remember this: A is for aging; B is for burn.

UVA: “A” is for Aging

UVA rays have the longest wavelength. Most of these rays are not absorbed by the ozone layer, so they account for over 90% of the UV radiation that reaches the earth. UVA rays also penetrate deeper into the skin, potentially causing many types of damage. They are responsible for the cumulative effects of sun- related skin aging, suntans (which are the skin’s natural reaction to the DAMAGE UVA rays cause to its DNA), and can lead to skin cancer.

UVA rays can easily penetrate clouds and glass, so they can also affect your skin indoors and on cloudy days. They are present whenever there is daylight, a near constant threat to the skin all day in all seasons of the year. They are the primary rays used in tanning beds and booths, which dangerously accelerate the aging of skin and its susceptibility to skin cancer.

UVB: “B” is for Burning

UVB rays are the shorter of the two. The ozone layer absorbs most of these rays, and those that get through penetrate only the top layers of the skin. UVB rays are primarily what cause sunburns, and they vary in strength depending on the time of day and season of the year – though you can get a sunburn in any season.

The Danger You Can Do Something About

The long-term, cumulative damage from year-round UVA rays takes time to reveal itself. Suntans, which are an indication of the damage starting, are still viewed as positive and attractive, DESPITE warning of the physical consequences yet to come. Eventually you’ll see these in the form of wrinkles, sagging skin, age spots, and possibly skin cancer – much earlier than you may have thought.

Photoaging – or aging caused by the sun’s rays – can happen any time you can see the light of the sun, whether you’re driving your car, getting your mail, exercising, etc.

You’ll notice that the skin of your hands and face probably looks older than the rest of your body. During colder months, you likely cover up most of your body to stay warm. Your face and hands are left exposed to the UVA rays that remain powerful all year long. After repeating this year after year, those parts of your skin begin to noticeably decline. Age spots and wrinkles appear, the collagen and elastin break down, and your skin loses its ability to repair itself.