Many people still don’t use sunscreen correctly, dermatologists say. Here are seven truths you may not know:

Sunscreen takes time to start working. Instead of slathering on lotion when you’re already outside, apply it 20 to 30 minutes before leaving the house.

A high SPF isn’t failsafe. Even products with SPF 50 or higher won’t block all of the sun’s rays. No matter how high the number on the bottle, you need a thick coating and reapplications every one to two hours.

It’s never too late to protect yourself. Even if you’ve had frequent sunburns in the past, you can still reduce your risk of skin cancer now. Daily sunscreen use will slow the growth of existing precancerous sun spots as well as reduce the number of new ones.

Self-tanner doesn’t help shield skin. For complex chemical reasons, staining your skin before heading out into the sun can make you more susceptible to damage. If you want to self-tan, apply the color the night before — and then put on a regular coat of sunscreen during the day.

You can have a base tan and still burn. Even if you look like a bronze god, don’t skip the sunscreen.

You can put sunscreen near your eyes. In fact, five to 10 percent of all skin cancers appear on eyelids. Carefully rub regular sunscreen on your lids or look for specially formulated products for sensitive facial skin, and wear a wide-brimmed hat.

Sunscreen doesn’t increase sweating. Research instead has found it can temporarily cool you down by blocking the sun’s rays from penetrating your skin. If lotions do bother you, especially during exercise, try sunscreen sticks which are waxier and won’t run.