But, after swimming, sweating or towel drying, you should reapply immediately. For best results, use at least one ounce of product per use to cover your body. So SPF 15 means you could stay out 15 times longer with sunscreen than without sunscreen. However, SPF refers to the amount of protection you get from UVB rays only. UVB rays are primarily responsible for burns and UVA rays are primarily responsible for the signs of aging.
Excessive washing can irritate already inflamed skin.
A good practice is to wash your face no more than twice a day. Don't use harsh soaps which may contain ingredients that actually cause acne or lead to skin irritation, especially for those with sensitive skin. Just because foods are oily or fatty doesn't mean they cause acne. In fact, no scientific studies have ever shown that foods bring on breakouts. So as long as you are not allergic to high-fat foods like french fries, pizza or chocolate and they do not irritate your skin, go ahead and eat them in moderation.