How to Choose – and Use – a Sunscreen

by Amy Tudor Patient Expert

Choices, choices...

There are many choices of sunscreens--almost too many! So how can you know if the sunscreen you've purchased is going to give the best protection against both sunburn and skin cancer?

In this slideshow, experts offer tips for choosing and properly using a sunscreen, including information on those SPF numbers and "rules of thumb" for applying--and reapplying--these products.

Understand the numbers

Sunscreens work by either absorbing or blocking UVB and UVA solar radiation. A sunscreen's SPF rating refers to its ability to absorb UVB rays and prevent them from damaging skin. Though there is no method to measure a sunscreen’s ability to absorb UVA radiation, products that block UVB are thought to block UVA too. Thus, the higher a sunscreen's SPF rating, the more radiation it's absorbing and the better it's protecting your skin.

Check the ingredients

An effective sunscreen should have an SPF rating at of least 15 and contain the ingredients avobenzone, titanium dioxide, or zinc oxide. Zinc oxide tends to be more opaque, and is thus not as cosmetically desirable. Newer sunscreens will be less obvious. As for expiration dates, sunscreens remain at full strength for up to three years. If your sunscreen is past its expiration date, replace it.

Wear enough of It

Most people apply only 25 to 50 percent of the amount recommended to protect their skin. Experts suggest that sunscreen users should apply enough of the product that they can actually see it as a whitish film on the skin.

Also, remember that it can take up to 30 minutes for it to be absorbed, so make sure you apply it about a half an hour prior to going out in the sun.

Reapply it often

Some experts you should reapply sunscreen every 20-30 minutes, while others say every 2-3 hours will be enough. This means reapplying the product within this 30-minute to 3-hour window of time is a good rule of thumb. And you should always reapply sunscreen after toweling, sweating excessively, or swimming.

Amy Tudor
Meet Our Writer
Amy Tudor

Amy wrote for HealthCentral as a patient expert for Psoriasis.