Cosmetics are very safe for the most part. The most common injury from cosmetics is from scratching the eye with a mascara wand and eye infections may result if the scratch goes untreated. These infections can lead to ulcers on the cornea or in the extreme worst case, blindness. To play it safe, never try to apply mascara while riding in a car, bus, train, or plane. But we see this done all the time. Sharing make-up can also lead to serious problems. Cosmetic brushes and sponges pick up bacteria from the skin. And if you moisten brushes with saliva, the problem can be worse. This is why brushes and sponges are usually treated with a bactericide prior to delivery with the end product. It is also why preservatives are added to cosmetics in the first place. Washing your hands before using make-up will help prevent this problem. Sleeping while wearing eye make-up can cause problems too. If mascara flakes into your eyes while you sleep, you might wake up with itching, bloodshot eyes, infections, or eye scratches.