More Culture:

June 29, 2016

Infrequently Asked Questions: What SPF sunscreen should I really be using?

By now, sunbathers know to lather up with sunscreen before a day on the beach. But is SPF 100 sunblock really protecting your skin better than the one labeled SPF 30? If so, how much better?

Eager for some insight as the summer sun sets in, we reached out to Dr. Nazanin Saedi, director of Jefferson's Laser Surgery and Cosmetic Dermatology Center, for an answer.

What is the ideal SPF? And what SPF is almost excessive?

  • The world is full of questions we all want answers to but are either too embarrassed, time-crunched or intimidated to actually ask. With Infrequently Asked Questions, we set out to answer those shared curiosities.

The [American Dermatological Association] recommends an SPF of 30 or higher. So, an SPF of 30 blocks about 97 percent of the sun’s UVB rays, and SPF 50 blocks 98 percent. So [the difference] is minimal. We recommend 30 or above. But the reason we don’t recommend 15, is 15 only blocks about 93 percent of the sun’s UVB rays.

How much is SPF 8 helping?

That would probably be not even 90 percent. It still does block some, but not as much as we’d like. The important thing is as high as you go, no sunscreen can block 100 percent of the UVB rays.

And what are those rays?

So visible light is made up of UVA rays and UVB rays. What we want to do is to ideally block both of them, because UVA can cause signs of aging and wrinkling of the skin, and UVB is really what causes the burns. What we recommend is using something that protects against both UVA and UVB, because you can prevent skin cancers and sunburn and early signs of aging.

What's the difference between sprays and lotions?

The sprays are easier to use, but really [don’t have as much] getting onto your skin. Whenever we use a product in dermatology, the thicker the substance is, the more your skin absorbs it. Ointments are greasier than creams which are thicker than lotions. So the thicker it is the better absorption it has into your skin; if you think about the sprays, they’re so light that your skin’s not absorbing as much as a cream would be.

What’s the agent in cream or spray to begin with that protects skin?

It depends. So, some common agents that are in sunscreens are oxybenzone — a main ingredient in sunscreens used for UVA and UVB — and, sometimes, retinol products are in sunscreens. That can be retinyl palmitate, and that’s good — it’s a derivative of Vitamin A and can protect our skin from signs of premature aging. So this is actually derivative of a retinoid, or retinae, which we’ve used for decades to prevent skin cancer among patients who have a high risk of developing skin cancers.

What determines the actual number on the label?

It has to do with how much of a difference, how much of a factor — how many times more protection it is offering you for preventing a sunburn. The things we look for is not just what the SPF is, but we tell people to look for sunscreens that are broad spectrum, so you’re getting the benefits of UVA coverage and UVB coverage.

Have you had any patients come in with sunburns?

It’s actually shocking because some come in with sunburns and peeling skin. And sometimes those are patients who are coming in for surgery for skin cancer. It’s really interesting. If it were me, personally, I’d probably make up an excuse to cancel and reschedule. I’d be embarrassed. [Laughs.]

What happens that causes your skin to peel?

You’re necrosing or causing basically cell death at the top layer of skin, so it’s peeling off. It does direct damage.

Are there areas of the body more susceptible to burns than others?

Well, certain areas that stick out that are not protected are areas we want patients to wear sunscreen. A lot of people wear baseball hats so their ears are exposed to the sun and not protected by the hat; it’s an area where people forget to put sunscreen on.

Anything you want to add?

Just basically how important it is to wear [sunscreen]. There's been so much negative press about 'Is sunscreen safe?' or 'Are we introducing toxins into our skin and causing more harm than good?' And sunscreen is safe — they are FDA-regulated, and there's no evidence in the literature to show it's toxic to humans.

Particularly with the sprays.

Yeah. There's no real data to show that.

Have a question you're dying to have answered? Send an email to, and we'll find an expert who can give you the answer you're craving.