Many of my patients are dismayed when I tell them that their high SPF sunscreen is not protecting them very well. I am a proponent of sunscreen, but real life use of sunscreen doesn’t give you the protection level on the bottle and this is why:
We don’t apply enough. In order to get the protection on the bottle, a person must use a whole teaspoon on their face. For covering the body (such as when in a bathing suit) an entire ounce needs to be used. Nobody uses this much because it would require multiple layers of sunscreen in order to avoid having sunscreen dripping off your skin.
We don’t reapply with enough frequency. Sunscreen needs to be reapplied every 2 hours and after swimming or sweating. In real world terms this would mean going through a bottle of your tinted moisturizer every 1-2 weeks and a whole bottle of sunscreen every day (per person) when on a beach vacation.
We use old sunscreen. How many of you have sunscreen bottles from 2010? Sunscreen breaks down and is not effective when it is old. Your sunscreen should be replaced every year. However, if you are using enough, your bottle should run out well before the year is up. If your sunscreen is separated, clumpy, smelly or just old- get a new bottle.
Sunscreen is not 100 percent protective. Even if you are applying enough sunscreen and reapplying, sunscreen still lets a percentage of UV light through. This small amount of UV light is enough to stimulate dark spots in people who are sensitive. If you have melasma, sunscreen is not enough to keep your face clear.
Sunscreen is a great tool to protect against skin cancer and photo-aging. However, we cannot depend on it to protect us 100 percent. When you put on sunscreen in the morning assume you are getting about half the SPF on the bottle. If your bottle says SPF 30, then your effective SPF at the moment you put it on is SPF 15. This number decreases as the day goes on, so at the end of the day (when you are sitting on the deck at happy hour) you likely have very minimal (or no) sun protection.
As we go into spring and summer, keep wearing sunscreen, but remember to reapply and consider other sun protective measures such as hats, clothing and shade. You’ll see me under the umbrella with my big hat and long sleeve shirt.