Should I test a sunscreen product before I use it?
Absolutely. Apply a small amount (about the size of a pea) to the inside of your wrist or the crook of your elbow. Don’t wash the area for 24 to 48 hours, and watch for any allergic reaction such as itchiness, redness, flaking, pain, or a rash or breakout of any kind.
A small number of people are prone to photoallergic contact dermatitis, a skin reaction that occurs when the sun activates an allergen found in sunscreen, perfume or medication. If you experience such a reaction, you can request a patch test from an allergist to identify the problem ingredient and avoid products that contain it.
How much sunscreen should I use?
To ensure that you get a sunscreen’s full SPF value, apply 1 oz. – about a shot glass full – to your face and the exposed parts of your body. Most people tend to apply only half to a quarter of that amount, which means the SPF they’re getting is lower than it should be. During a long day at the beach, use around a quarter to a half of an 8-oz. tube or bottle.
Where, exactly, should I apply it?
Apply sunscreen evenly to all uncovered skin, paying special attention to your lips, nose, ears, neck, hands and feet. If you don’t have much hair, apply some to the top of your head, or wear a hat. And remember, never apply sunscreen to damaged or broken skin. Instead, wear bandages or protective clothing over those areas to avoid infection, while still protecting the skin from sun rays.
How often should I use it?
Apply sunscreen about 30 minutes before sun exposure to allow the ingredients to fully bind to your skin. Make sure to reapply the same shot glass dose every two hours—and also immediately after swimming, toweling off or working up a sweat.