A Guide to Sunscreen Terms

Protecting your skin from sun damage is one of the most important preventive skin measures. Our guide below will help you understand the differences for each term. What’s the difference between UVA and UVB, or water-resistant and waterproof? Is SPF 80 really that much better than SPF 30? What are nanoparticles and how do they affect you? Unlock the mystery of your sunscreen’s label by learning these important terms.

1. SPF
(Sun Protection Factor)

A measure of how much UVB radiation it would take to burn protected skin (with sunscreen) relative to the amount required to burn unprotected skin (without sunscreen). Let’s break it down. For example, if your skin normally burns after 10 minutes in the sun, an SPF 15 would allow you to stay in the sun without burning for approximately 150 minutes or 15 times longer.

So does that mean SPF 80 is that much better than SPF 50? The FDA says there’s not enough data to support that, so its most recent ruling limits the maximum SPF value on sunscreen labeling to “SPF 50+.”

2. UVA (Ultraviolet A)

Accounts for up to 95 percent of the UV radiation reaching the Earth’s surface. They are less intense than UVB, but they penetrate the skin more deeply and play a major part in skin aging and wrinkling.

3. UVB (Ultraviolet B)

The shorter of the two UV rays and more intense, especially between 10 a.m. and 4 p.m. UVB damages the skin’s more superficial epidermal layers, causing skin reddening and sunburn. It plays a key role in the development of skin cancer.


Means that the sunscreen provides protection against both UVA and UVB rays.


Protects your skin by using chemical filters to absorb UV light. Commonly used chemical filters include avobenzone, oxybenzone, Mexoryl SX and XL and Tinosorb M.


Often appearing white, it works by deflecting or blocking the sun’s rays with mineral filters zinc oxide and titanium dioxide. Believed to be less irritating than chemical sunscreens because they don’t penetrate the skin and contain less irritants and allergens. Also known as physical sunscreen.


Doesn’t degrade or change its form when exposed to sunlight.


The ability of the sunscreen to stay on the skin—and maintain its SPF level—after 40 to 80 minutes of water exposure. The FDA only allows the claim “water-resistant” on sunscreen labels because it believes no sunscreen can rightfully claim to be “waterproof.”


Particles that measure less than 100 nanometers in diameter. Some sunscreen ingredients—like zinc oxide—are reduced to this size so the sunscreen dries clear instead of white. Some consumer and environmental groups have raised concerns about the health risks of nanoparticles, though recent studies revealed that nanoparticles are considered safe.


Means the product will not clog your pores—an important factor to consider if you have oily, sensitive or acne-prone skin.


The most dangerous type of skin cancer and the leading cause of death from skin disease. 


Flat, brown or black spots that appear on the areas of the skin exposed to the sun, particularly the face, hands, shoulders and arms. Also known as age spots, liver spots or solar lentigines.


Unstable molecules that create damage by stealing electrons from healthy cells. Sun exposure generates free radicals and causes premature aging.


Generally refers to the damage done to the body and skin by prolonged exposure to UVA and UVB radiation.


Neutralizes free radical damage. When paired with a potent sunscreen, antioxidants up your defense against the sun.

Check out all the sunscreen products on Chosenmeds.com available here.