All this begs the question: Should you apply the product like a serum (post-cleansing, pre-moisturizer) or like a standard sunscreen (usually the last step of your routine). The answer, I’m afraid, isn’t so cut and dried. 

“I would recommend applying after cleansing, before moisturizing,” says King (aka, treat it like a serum). That way, all those active ingredients can easily penetrate the skin and treat those targeted concerns. However, if your serum contains physical blockers—like zinc oxide or titanium dioxide—it may make more sense to apply it last, especially if you’ve already applied a favorite serum during your treatment step. Essentially, it all chalks up to user behavior.  

But perhaps more important than the when is the how much: Since a sunscreen serum has a thinner consistency than a lotion, how much product should you use to ensure you’re getting maximum protection? According to King, you should still use a nickel-sized dollop of sunscreen to achieve the advertised SPF on the label, no matter the type of product—serum, tinted moisturizer, what have you. 

“Unless you’re going to use this much of the serum, then think of it more as a way to layer SPF,” she adds. “It’s a fine way to start but make sure to follow with additional SPF steps to ensure good protection.” For example, you could use the sunscreen serum after cleansing, then follow with a lotion at the end of your routine. Or if your sunscreen serum contains color correcting tint (some options toe the line between skin care and makeup), you can layer it on top of your lotion for a subtle glow. 

And let’s not forget, proper sun protection extends much farther than sunscreen: Even if you pile on SPF, you still need to be smart about your time under the sun