We all know the rule of thumb when it comes to sunscreen: Wear it all day, every day. However, that being said, the topic of wearing sunscreen with makeup is not so cut and dry, as it brings up a series of questions and concerns. What level of protection do you really need? Should you reapply? Is SPF in foundation enough? We could go on and on, right? Here to help us practice safe-sun (and settle our burning curiosity!) is New York City-based dermatologist, Dr. Bruce Katz of Juva Skin.

Simple - "SPF 30," says Dr. Katz. "I tell my patients to apply it evenly all over until it vanishes. And for both UVA and UVB protection, it's important to look for these three ingredients: Zinc Oxide, Titanium Dioxide and Avobenzone," he says. Don't forget to apply some to your neck and ears!

Hey! Your makeup already has SPF in it, so that should have you covered, right? Wrong. "Don't rely on makeup for the best source of SPF as it's notoriously unreliable in terms of the level of protection. Plus, makeup isn't always applied evenly and comes off easily - thus, decreasing optimal coverage. You want to wear sunscreen underneath your cosmetics and it actually provides a better base for your makeup application," says Dr. Katz.

He also recommends waiting a few minutes before applying your foundation, so as to allow your sun protection to set and really penetrate the skin!

That depends. "If you're sweating or swimming, I recommend that you reapply sunscreen every two to three hours, but if you're not getting wet, it can last four to six hours," says Dr. Katz. Now an answer to the question us beauty-lovers have been waiting for - how do you reapply SPF when you're already wearing makeup?

"For maximum protection, sunscreen should be applied directly onto skin, underneath any makeup, other moisturizers or skincare products. You can put sunscreen on over your foundation, but ideally you would wash it all off and reapply - although, we know most women won't really do that," says Dr. Katz. Not unless we get to bring our whole beauty arsenal with us!

An alternative? Loose powder or a mineral veil with added sun protection like Lancôme Ageless Minérale With White Sapphire Complex or Giorgio Armani Lasting Silk UV Compact. Just don't forget to wear physical sunscreen underneath your makeup and avoid staying near windows for long periods of time in the office!

What's your daily SPF routine and how often do you reapply? Let us know in the comments below!

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