Reapplying sunscreen may feel like a hassle, but it's an essential step for maintaining skin health. Why is it necessary?
One application won’t last you the whole day. The protective agents in sunscreen break down as they work to protect your skin. Once they have broken down, your skin is no longer protected. In addition to this, being in water or sweating washes sunscreen away over time, leaving your skin exposed. Water-resistant sunscreens can stay on longer, but they still need to be reapplied. The same thing goes for sunscreens with higher SPFs. No matter how high the SPF is, you will still need to reapply your sunscreen.
The general rule is to reapply every two hours. You should especially focus on following this if you are in the sun for extended periods of time, whether it be outdoors or facing a window and if you’re sweating or in water. Facing windows may not seem like a big deal, but harmful UVA rays can still pass through windows and damage your skin. However, if you're going to be indoors and not facing any windows, it's safe to say you won't need to reapply for the time being.
Also, make sure that you’re applying the directed amount of sunscreen to reap the full benefit of the product. Most sunscreens require you to apply a nickel-sized amount for your face and two tablespoons for your entire body, but that can change depending on the product, so always read the label. Most people don't apply enough sunscreen, so regularly reapplying can also help compensate for any potential underapplication.