All energy in the universe exists in a form of radiation. Radiation can be safe when it is in the form of visible light, radio waves, microwaves, and infrared rays, and extremely dangerous when in the form of gamma rays. The electromagnetic spectrum is the measure of all types of radiation found in the universe, and ultraviolet (UV) radiation (which is emitted from the sun) is included in the spectrum. One day of exposure to UV radiation is extremely unlikely to cause any long-term effects, but over a lifetime, the photo-aging effects of the sun will manifest in the form of wrinkles, dryness, age spots, and sagging skin.
UV-A Rays: The "A"ging Radiation
The radiation from the sun reaches your skin in two forms: UV-A and UV-B. UV-A rays are responsible for the photo-aging effects seen from prolonged, unprotected sun exposure. UV-A rays penetrate deeper into the skin than UV-B rays, causing damage to skin cells such as keratinocytes, which reside in the basal layer of the epidermis, where most skin cancers are formed (Source: Skin Cancer Foundation).
In addition to causing skin cancer, exposure to UV-A rays can also lead to wrinkled, sagging skin, dryness, and age spots
In a study conducted on mice exposed to UV-A radiation over 6 weeks with no protection, it was found that the mice developed severe and deep wrinkling on the skin's surface compared to mice not exposed to UV-A radiation (Untreated).
One of the identified reasons for the significant aging effects from UV-A exposure was the loss of elastin, a protein that gives your skin cells its 'elastic' quality. Without elastin, your skin would have a sagging, 'worn out' appearance. Note the shrunken, sagging, and degraded appearance of the elastin fibers in the UV-A exposed samples compared to the untreated (unexposed) samples.
UV-B Rays: The "B"urning Radiation
At some point, most people will experience a sunburn. Sunburns are the immediate painful result of prolonged, unprotected sun exposure, and are caused by UV-B rays. UV-B rays can only penetrate the top layer of skin, producing a red, burning effect. Like UV-A rays, UV-B rays are also a culprit for skin cancer and photo-aging.
Proper Sun Protection and Choosing the Correct SPF for Your Skin
Sun protection primarily comes in two forms: physical and chemical. Physical sun protection includes wearing a hat to protect your scalp and face, and clothing to cover the rest of your body. Chemical sun protection is the use of sunscreen to ward off the sun's rays. Using both physical and chemical sun protection is your best bet to avoid the harmful effects of ultraviolet radiation.
Most do not have a problem picking out physical sun protection, such as a hat, or long sleeved shirts, but there is a significant amount of confusion and among consumers when picking out the right sunscreen. The confusion mainly resides in two areas: active ingredients and SPF.
Active Ingredients in Sunscreen
The FDA currently approves of 17 active ingredients to be used in sunscreen. Some of these ingredients, such as avobenzone, only protect against UVA rays, some ingredients, such as homosalate and aminobenzoic acid, only protect against UVB rays, and other ingredients, such as oxybenzone, titanium dioxide, and zinc oxide, protect against both UVA and UVB rays. Choose a broad protection sunscreen that has active ingredients that will protect against UVA and UVB rays.