Test Your Sunscreen Knowledge - Part 1

Originally published in SkinNews, Volume XVI, Issue 2, Fall 2009 by Richard G. Asarch, M.D.

1. The SPF notation on sunscreens measures the protection against the sun's ultraviolet B (UVB) radiation. SPF tells you:

a. How long it will take your skin to sunburn with sun exposure when using the sunscreen vs. how long it will take your skin to sunburn without sunscreen

b. The percentage of active ingredients in sunscreen

c. The number of hours you can stay safely in the sun

2. A sunscreen with an SPF of 15 protects against approximately 93% of the sun's UVB rays while a sunscreen with an SPF of 30 protects against:

a. 97% of the sun's UVB rays

b. 93% of the sun's UVB and UVA rays

c. 95% of the sun's UVB rays

3. A sunscreen with an SPF of 100 will protect against:

a: 100% of the sun's UVB rays

b. 99% of the sun's UVB rays

c. 97% of the sun's UVB rays

4. The FDA test for determining a sunscreen's SPF protection is based on a generous application of at least 2 ounces at a time. Realistically, most people do not apply that amount. At one-half of the recommended application amount, a sunscreen with an SPF of 30 would yield an SPF of:

a. 30

b. 15

c. 7-8

5. If you first apply a sunscreen with an SPF of 20 and then one with an SPF of 30, the effective SPF you have achieved is:

a. 25

b. 30

c. 50

Answers to questions 1-5:

1) a, 2) a, 3) b, 4) c, 5) b