To protect against sunburn, you should apply a sunscreen with a sun protection factor (SPF) of 30+ or more. Children and adults who are prone to sunburn should use a higher SPF. You should use a broad-spectrum sunscreen, meaning it will protect you against different forms of UV rays (UVA, UVB and UVC). Make sure the sunscreen is water-resistant. Apply it to clean, dry skin at least 20 minutes before you go outside, and then reapply every 2 hours. You may need to reapply it more often if you are swimming, sweating a lot or rubbing yourself dry with a towel. You need at least a teaspoon of sunscreen for each arm and leg, your back and your body. You need about half a teaspoon on your face and neck. Make sure your sunscreen has not passed its expiry date and hasn’t been stored in direct sunlight or hot temperatures such as in a hot car or by the pool, as then it may not work properly.