This page was reviewed under our medical and editorial policy by
Frederick L. Durden Jr., MD, Plastic and Reconstructive Surgeon & Microsurgical Reconstructive Surgeon.
This page was updated on October 19, 2022.
You’ve likely heard the message time and time again: You must apply sunscreen to protect your skin from the sun’s damaging ultraviolet (UV) rays. Using sunscreen is the best way to reduce the risk of developing skin cancer, including melanoma.
Natural sunlight is a major source of damaging UV rays, but there are other ways you may be exposed, too.
UV rays are a form of ionizing radiation, which means they have an elevated level of energy—enough energy to remove an electron from an atom or molecule. They damage the genetic material in cells, which may lead to cancer. The risk only runs skin-deep, though: They don’t tend to penetrate deeper than that, so the main risk of UV radiation is skin damage, including skin cancer.
The three types of ultraviolet rays are identified as UVA, UVB and UVC:
Ultraviolet A (UVA) rays are known to cause premature aging and wrinkles and may play a role in some skin cancers. These make up most of the sun’s rays that reach your skin.
Ultraviolet B (UVB) rays may damage the DNA or genetic material within skin cells. Registering a bit more energy than UVA rays, they’re thought to be responsible for most skin cancers. These make up about 5 percent of the sun’s rays that reach your skin.
Ultraviolet C (UVC) rays, the most dangerous, are absorbed by the ozone layer and don’t reach the Earth’s surface.
UVB rays stimulate skin cells known as melanocytes to produce melanin, causing a sunburn or tan, both of which are signs of damage. As many as 90 percent of melanomas are thought to be caused by UV exposure, and both basal cell and squamous cell cancers—the two most common skin cancers—are most often found on sun-exposed parts of the body, suggesting a strong causative role for the sun’s rays.
The sun is the main source of cancer-causing UV radiation, but it’s not the only one. Tanning beds and sun lamps also emit UV rays. The International Agency for Research on Cancer (IARC) has declared that use of UV-emitting tanning devices causes cancer in humans, as does UV radiation.
Indoor tanning may cause more than 400,000 cases of skin cancer in the United States each year, according to the American Academy of Dermatology Association.
Beyond tanning beds and booths, other man-made UV rays may come from different lighting sources.
Your skin type, when you were exposed to the sun, and whether you wore sunscreen all affect your chance of developing skin cancer. People with fair skin tend to be more susceptible to sunburns and the damage that leads to skin cancer, but those with darker skin may develop it, too.
Risk factors include:
Being exposed to UV rays at a young age may be particularly damaging. A history of sunburns in childhood increases skin cancer risk. Using tanning beds before age 30 raises the risk for melanoma by 75 percent, according to the IARC.
Skin cancer isn’t the only cancer caused by UV rays. They may also cause cancers of the eye and other eye issues, including cataracts.
When it comes to skin cancer, prevention is key. This starts with protecting against both UVA and UVB rays by using a broad-spectrum sunscreen with an SPF (Sun Protection Factor) of 30 or higher.
You should also:
Pay attention to warning signs, such as a new spot on the skin or one that’s changing size, color or shape. Use the ABCDE rule:
The ABCDE rules don’t cover all the potential warning signs, so inform your doctor if you notice anything that’s different or concerning.