UVA and UVB Rays: What’s the Difference?

UVA and UVB Rays: What’s the Difference?

In the summer of 2012, the FDA made some big changes to the regulations surrounding sunscreen labels, including making a distinction between the effects of UVA and UVB rays. Sunscreens that protect against both UVA and UVB are now labeled as “broad spectrum” while sunscreens that are are not broad spectrum and/or are between SPF 2 and 14 must contain the warning that “This product has been shown only to help prevent sunburn, not skin cancer or early skin aging” (FDA). The warning label gives a hint at the difference between the two types of UV rays, but to fully understand the differences between two of the most important terms in sun protection, first we need to understand what UV (Ultraviolet) radiation is.


UV radiation is part of the electromagnetic light spectrum that comes from the sun’s rays. The wavelengths differ in length, and are classified as UVA, UVB, and UVC. UVA is the longest, and UVC is the shortest, with most of it absorbed by the ozone layer before reaching earth. Both UVA and UVB penetrate the atmosphere and play an important role in conditions such as premature skin aging, eye damage, and skin cancers by damaging the skin’s cellular DNA.


UVA is the most pervasive of the sun’s rays, accounting for almost 95% of the UV radiation that reaches earth, including during the winter months and through glass panes. Although less intense than UVB rays, UVA penetrates deeper into the skin and plays a large part in skin aging and wrinkling. Studies in recent decades have shown that previous beliefs about its harmful nature were wrong, and the UVA does indeed contribute to the development of skin cancers. UVA is dominant tanning ray, and the one primarily used in tanning booths though in much higher doses than the sun. Studies have proven the dangers of tanning beds, and while regular sun exposure is less dangerous than the doses of tanning radiation, the danger is still present.


UVB rays are the rays we fear the most, causing sunburns and damage to the more superficial epidermal layers of the skin. The intensity of UVB varies between season, time of day, and location, and it does not significantly penetrate glass. UVB rays are especially dangerous at high altitudes and near reflective surfaces such as ice and snow.


Armed with the knowledge that both UVA and UVB exposure is bad for your skin’s health, make sure that your sunscreen is labeled as “broad spectrum”, meaning that it protects against both types of rays. Also take other precautions such as staying in the shade at peak sun times and wear protective clothing. The Hawaii Medicinal product line is broad spectrum, bouncing UVA and UVB rays off of your skin.