Dermatologist Dr. Ava Shamban Joins La Roche-Posay to Answer Top Questions about Sunscreen


We joined La Roche-Posay at Norah in West Hollywood to learn about what’s new in sensitive skin care and UV protection with tips from top dermatologist Dr. Ava Shamban. “The number one prevention method for premature aging is sunscreen,” says Dr. Shamban, who specializes in wrinkle reduction and other aesthetic skin care procedures. 


Dr. Shamban recommends La Roche-Posay’s sunscreens are because they are great for sensitive skin and they don’t contain harmful chemicals. The new Anthelios Sunscreen with Cell-Ox Shield is formulated with La Roche-Posay’s highly selective formulation. The fragrance-free, paraben-free mineral sunscreen is also in compliance with the new Hawaii state regulations.

“One of the beautiful things about La Roche-Posay sunscreen is that most of them are fully mineral-based,” she says. “The sunscreen is mostly zinc oxide and titanium dioxide. There are no chemicals in it. The other good thing about this sunscreen is that it’s very good for sensitive skin. The sunscreen also absorbs and blends well without leaving a powdery looking residue on the skin. “

Below, Dr. Ava Shamban answers some of the most common sunscreen questions":

How much much sunscreen should you apply?

We usually say a shot glass per limb. The SPF that is on the label is directly related to the quantity of sunscreen that you are applying You can never put on too much sunscreen.

How long does sunscreen last?

It depends on the specific one. You want to look to see whether it’s water-resistant or waterproof. If you’re applying sunscreen in the morning and you’re just going to be indoors, you should reapply once during the day. If you are outdoors and getting in and out of the water, you should apply directly after that (sunscreen is water-resistant for 80 minutes). The rule of thumb is to apply every two hours.

If you’re planning on applying a full face of makeup, when should you put on your sunscreen?

I put the sunscreen on first and use it almost as a moisturizer, then apply the makeup on top of it. Makeup with SPF is not as effective as sunscreen. (If you put on an SPF 30 on and then you put on makeup with an SPF of 30, it doesn’t equal 60. That’s not how it works.)  My rule of thumb is to apply the sunscreen first and then float the makeup on top of it.

How long does sunscreen last after you open it?

It depends on if you leave the top off, if it gets heated up, if you leave it in your car, etc. When any oxygen gets into a product, it’s getting oxidized which makes it less effective. It’s not that it goes bad, it just becomes less effective. If your sunscreen is lasting longer than that, it means you’re not using it enough!

Do people not need SPF if they are indoors all day?

Data shows that UVA rays penetrate through glass. And even some of the radiation comes off of computer screens. You don’t necessarily see the damage right away; it can take a while to see brown spots. UV does penetrate though glass—you can see the damage on people’s hands from exposure while driving.

Check out the latest products from La Roche-Posay at and follow them on Instagram: @larocheposay. Learn more about Dr. Ava Shamban at


Lizzy Sherman is an award-winning digital content writer/editor. She has been a featured guest speaker at Cal State University Northridge, Digital LA and The National Association of Audience Marketing Professionals. When she's not writing, Lizzy enjoys yoga and playing guitar. Follow her on Instagram: @zillizy