Ultraviolet (UV) radiation is the electromagnetic wave responsible for the vast majority of skin cancers. UV exposure is linked to roughly 90% of non-melanoma skin cancers (basal cell carcinoma and squamous cell carcinoma) and about 65% of melanoma cases. While other electromagnetic waves like X-rays and gamma rays can also cause skin cancer, UV radiation from the sun and artificial sources is by far the most common culprit.
Why UV Radiation Is the Primary Cause
The electromagnetic spectrum ranges from low-energy radio waves to high-energy gamma rays. UV radiation sits just beyond the violet end of visible light, in the 200 to 400 nanometer wavelength range. It’s divided into three types based on wavelength: UVA (315 to 400 nm), UVB (280 to 320 nm), and UVC (100 to 280 nm).
UVB is the most significant driver of skin cancer. It directly damages DNA in skin cells by causing neighboring molecules in the DNA strand to fuse together, creating errors the cell can’t always repair correctly. When these errors accumulate in genes that control cell growth, normal skin cells can become cancerous. UVB is also what causes sunburn, which is essentially visible evidence of DNA damage in your skin.
UVA penetrates deeper into the skin than UVB and causes damage through a different route. Rather than hitting DNA directly, UVA generates reactive oxygen molecules inside cells that damage DNA indirectly. UVA can also produce the same type of direct DNA damage as UVB, but it takes a far higher dose to do so. Because UVA makes up the bulk of UV radiation reaching the ground, its cumulative contribution to skin cancer is significant even though it’s less potent per unit of exposure. UVA is also the primary driver of premature skin aging.
What About UVC?
UVC is actually the most damaging type of UV radiation to living cells, but the Earth’s atmosphere filters it completely before it reaches the ground. The ozone layer, along with oxygen and water vapor, absorbs all UVC and most UVB from sunlight.
The concern with UVC comes from artificial sources. Germicidal lamps used for disinfection emit UVC, and accidental exposure can cause burns, eye damage, and cellular changes in skin. The International Agency for Research on Cancer classifies all UV radiation, including UVC, as a Group 1 carcinogen (meaning there is sufficient evidence it causes cancer in humans). Research on germicidal lamps has shown that even seconds of direct exposure can cause irreversible damage to skin cells and eye tissue. Skin cells called keratinocytes are somewhat resistant to immediate cell death from UVC, but they become prone to a state called senescence, where they stop functioning normally, a process linked to long-term cancer risk.
X-Rays and Gamma Rays Also Carry Risk
Higher-energy electromagnetic waves, specifically X-rays and gamma rays, are ionizing radiation. They carry enough energy to strip electrons from atoms and directly break DNA strands. Therapeutic radiation exposure has been linked to roughly a threefold increased risk of both basal cell carcinoma and squamous cell carcinoma at the site where radiation was delivered. A Canadian population study found a five- to sixfold increase in skin cancer incidence associated with non-diagnostic X-ray exposure.
The risk from medical X-rays in routine imaging (a chest X-ray or dental scan) is extremely small because the doses are low and the exposure is brief. The elevated skin cancer risk applies primarily to people who received repeated or prolonged radiation therapy, particularly those treated for conditions like acne with radiation (a practice that has largely been abandoned). People with sun-sensitive skin who had radiation therapy showed the highest risk for squamous cell carcinoma.
How the UV Index Affects Your Risk
The UV Index is a scale that measures how strong UV radiation is at a given time and place. When the index is 3 or higher, your skin is accumulating meaningful damage even if you don’t feel it. At a UV Index of 11, lighter skin tones can burn in under 5 minutes. But burning isn’t the only signal that matters. Darker skin tones that don’t burn easily still absorb invisible radiation damage that affects DNA over time.
Sunscreen works primarily by absorbing UVB. SPF 15 blocks about 93% of UVB, SPF 30 blocks about 97%, and SPF 50 blocks about 98%. The jump from SPF 30 to 50 is only about one percentage point of additional protection, which is why dermatologists generally recommend SPF 30 as a practical baseline. Look for “broad spectrum” on the label, which means the product also provides UVA protection.
Medications That Increase UV Vulnerability
Certain common medications make your skin more sensitive to UV damage, a side effect called photosensitivity. If you take any of the following, your threshold for UV-related skin damage is lower than normal:
- Antibiotics: particularly tetracycline and doxycycline
- Common pain relievers: ibuprofen, naproxen, and other anti-inflammatory drugs
- Blood pressure and heart medications: certain diuretics like hydrochlorothiazide
- Cholesterol-lowering drugs: statins including simvastatin and atorvastatin
- Acne treatments: isotretinoin and other retinoids
- Oral contraceptives and estrogen therapy
- Some antihistamines: including cetirizine, diphenhydramine, and loratadine
- Diabetes medications: certain oral drugs for type 2 diabetes
- Skincare products containing alpha-hydroxy acids (AHAs)
Photosensitivity from these medications means UV radiation can cause more severe burns and potentially more DNA damage at lower exposure levels than you’d normally experience. If you’re taking any of these, extra sun protection becomes more important.
The Bottom Line on Electromagnetic Waves and Skin Cancer
UV radiation, especially UVB, is responsible for the overwhelming majority of skin cancers worldwide. X-rays and gamma rays can cause skin cancer too, but only in the context of significant or repeated medical radiation exposure. Radio waves, microwaves, infrared, and visible light do not carry enough energy to damage DNA and are not linked to skin cancer. The practical takeaway is straightforward: the electromagnetic wave you encounter most often and need to protect against is ultraviolet radiation from the sun.