Ultraviolet Light – the Good, the Bad, and the Ugly
March 17, 2015 | By Venessa Peña-Robichaux, MD
Ultraviolet (UV) light makes up a small portion of the sun’s rays and is the major cause of skin damage. Exposure to UV rays causes damage to DNA in skin cells, increases the risk of skin cancer, and accelerates signs of aging (fine lines, deep wrinkles, dark spots, etc). There are three types of UV light: UVA, UVB and UVC. Let’s look at their differences and how they affect the appearance and health of your skin.
UVA: UVA light is not absorbed by the ozone layer and is able to penetrate the dermis in humans, which is the deepest layer of skin. UVA rays cause many effects on the skin including immediate skin redness and darkness, formation of fine lines, wrinkles and age spots. UVA plays a minor role in the development of skin cancer because it causes formation of free radicals in the skin. It is able to penetrate glass (windows), which is why wearing sunscreen on a daily basis is recommended, even if you don’t go outdoors. A great example of the advanced skin aging that can be seen with daily exposure to UVA can be seen in the photo below that was published in the New England Journal of Medicine. The man in this photo was a truck driver for 25 years and you can easily see that the left side of his face has thicker skin and deeper wrinkles.
Remember, UVA = Aging
UVB: UVB is another form of UV light and not all UVB reaches the earth because some rays are absorbed by the ozone layer. Because UVB rays are shorter and have a higher frequency, they are more damaging to skin as they penetrate the epidermis (top layer of skin). UVB radiation causes sunburns and delayed tanning. It plays a major role in the development of all types of skin cancers causing DNA damage to skin cells and the immune system. UVB is also important in the synthesis of Vitamin D3.
Remember, UVB = Bad Burns
UVC: UVC rays are too short to get through the Earth’s atmosphere. Although UVC is the most dangerous form of UV radiation, it is completely absorbed by the ozone layer and does not normally cause skin cancer.
Of course, the amount of UV light that reaches a person at any given time and place is dependent on many factors including the time of day, time of the year, elevation, and cloud cover. The UV Index (ranges from 1-11+) is something one can refer to see how intense the UV light is in the area. A higher number means greater exposure of UV rays and a higher risk of sunburn and skin damage. For the daily UV index in Austin, click here.
What’s the difference between a tanning booth and phototherapy treatment?
I often have patients ask me this question because dermatologists make a big deal about avoiding outdoor sun exposure and tanning booths at all costs. “Why shouldn’t I use a tanning booth if you have a tanning booth in your office?” Tanning booths and phototherapy booths are very different. Here are the facts:
- Most tanning booths give off primarily UVA rays
- 20 minutes spent in an indoor tanning booth equals about 2-3 hours in the noontime sun
- People who first use a tanning bed before age 35 increase their risk for melanoma by 75%
- People who use tanning beds are 2.5 times more likely to develop squamous cell carcinoma and 1.5 times more likely to develop basal cell carcinoma
- The Federal Trade Commission has ruled against claiming health benefits for indoor tanning
- Phototherapy is light therapy that is prescribed and administered by a dermatologist in their office. Treatment involves exposing the skin to an artificial UV light source for a set length of time on a regular schedule.
- Nowadays, the most common type of phototherapy used is called narrowband UVB; ”narrowband” refers to a specific wavelength of UV radiation that is safe for the skin.
- Narrowband UVB has anti-inflammatory effects on the skin and is used to treat many skin conditions such as psoriasis, eczema, vitiligo and even some types of skin lymphomas.
- There is no evidence to suggest that broadband or narrowband UVB treatments increase the risk of skin cancer.
What about Vitamin D?
While it is true that exposure to sunlight (specifically UVB) helps to produce Vitamin D3 in your body, the amount of sunlight that you actually need for adequate levels of Vitamin D is minimal. About 5-10 minutes of exposure to the arms and legs OR hands, arms and face 2-3 times per week is sufficient for healthy Vitamin D levels. This is especially true if you eat foods that are high in Vitamin D (i.e. fish, mushrooms, tofu/soy, dairy, eggs) and/or take oral Vitamin D supplements. Because it is not uncommon for some people to have low Vitamin D levels, especially in areas of the country that tend to be overcast during most of the year, most physicians now recommend daily oral supplementation. This is especially important for women who are at increased risk of developing osteomalacia/osteoporosis. Currently the recommended dose of Vitamin D for the general population is 600 IU for those 1-70 years of age and pregnant or breastfeeding women, and 800 IU for those over 71 years of age.
What can I do to protect myself?
The lesson to learn here is that sunlight is not the enemy but rather the conduit of an unavoidable exposure (UV radiation) that we must learn to control. I myself love being active outdoors on a nice sunny afternoon. On days such as these when we venture out to enjoy nature we can protect our skin by trying to linger in shaded areas, wearing sunscreen on exposed areas of the skin (minimum SPF of 30, reapplying every 1-2 hours) and wearing photoprotective clothing (wide brimmed hats, sunglasses, breathable long sleeved shirts, etc).
For everyday protection I recommend using a moisturizer with sunscreen on the face, neck and chest. Minimizing exposure to UV radiation through these measures is one of the best things we can do for our skin in order to decelerate the signs of aging and prevent skin cancer.