The primary purpose of lip balm is to provide an occlusive layer on the lip surface to seal moisture in lips and protect them from external exposure. Dry air, cold temperatures, and wind all have a drying effect on skin by drawing moisture away from the body. Lips are particularly vulnerable because the skin is so thin, and thus they are often the first to present signs of dryness. Occlusive materials like waxes and petroleum jelly prevent moisture loss and maintain lip comfort while flavorants, colorants, sunscreens, and various medicaments can provide additional, specific benefits. Moisturizers but can also be made at home using common pharmacy ingredients. Moisturizers can be used to prevent the skin from becoming too dry or oily, such as with light, non-greasy water-based moisturizers. Such moisturizers often contain lightweight oils, such as cetyl alcohol, or silicone-derived ingredients, such as cyclomethicone.