Habit: Wearing Sunscreen All Day, Every Day

This one is a bit more controversial, as not all dermatologists agree. Some believe you should wear sunscreen every day, no matter how much sun you expect to get. Others think that the only people who need to be religious about sun protection are at-risk skin types: the exceedingly fair, those prone to freckling, people for whom cancer runs in the family, and those who spend tons of time outdoors.

According to Dr. Ostad, it's really not necessary to slather on the SPF 35 unless you're going to be outside for a prolonged amount of time (read: longer than it takes you to walk from your subway stop or car and into your office). Besides the whole vitamin D deficiency issue, Ostad says that piling on sunscreen can cause a build-up of oil and leave a product residue on your skin, leading to increased oiliness and breakouts. We think this is one of those scenarios where you have to take your specific needs and situation in mind and decide what's best for you.

Photo: Maria Valentino/MCV Photo