Physiologically unique, the lips are predisposed to be the driest spot on our face or body. While the face is covered in a relatively thick, protective layer of skin, the lips are vulnerable in comparison. The top corneum layer of the lip is about 3-4 layers thick (very thin) when compared to typical facial skin that generally has 15 to 16 layers.
Skin on the lips has no hair follicles or sweat glands. Therefore, it does not have the ability to sweat nor any body oil production to assist in protecting the lips from environmental extremes. Lip skin contains very few melanin cells. Because of this, blood vessels appear more clearly through the skin of the lips giving them their characteristic pinkish hue. This also explains why, in cold weather conditions, the lips may turn blue or purple as blood flow is diverted away from the face to the vital organs. Due the differences in the structure of lip skin, the lips dry out faster and become chapped more easily than the rest of the body.
One way to protect lips is through the frequent use of fats, oils and waxes in the form of lipsticks or balms. Generally, lipstick is used as a method of conveying cosmetic colors to the lips and lip glosses or balms are used as a method of moisturizing or protecting the lips with a barrier. Some glosses and balms still contain a hint of color, but their general purpose is as a protectant.
Many of the colors used in lipstick and other cosmetics are also used in food. Because of this, color safety came under increasing scrutiny during the twentieth century to ensure that colorants were free from any toxic or irritating ingredients. This was particularly important for lip cosmetics as these can be ingested through daily wear. In the United States, certified lists of colors that can be used in cosmetics (D&C; F,D&C) are published by the Food and Drug Administration (FDA). As colors are added or deleted from this list, cosmetic manufacturers are required to make adjustments to their formulations. Only colorants that are approved for use on the lips are permitted to be used in lip cosmetics and it is the formulators’ responsibility to ensure that only approved colorants are used for this purpose.
Lip cosmetics differ from other forms of make-up in that they are tasted as well as smelled, therefore both fragrance and pleasant flavor need to be considered when selecting aroma compounds. Many raw materials commonly used in lip cosmetics, such as lanolin, beeswax and castor oil have a natural odor and flavor that can be off-putting or even offensive to consumers. Luckily, these odors and flavors can be disguised.
Since lip cosmetics are used in close proximity to our noses, the need to mask odiferous ingredients is common. As with other color cosmetics, not all aromatics are suitable for use on the lips as many can irritate the sensitive lip tissue or have a disagreeable taste. One solution to this issue is to include flavors and sweeteners in lip cosmetics. Usage of flavors is controlled by the Food & Drug Administration (FDA) and The International Fragrance Association (IFRA).
Because of the delicate physiology of the lips it is imperative that formulators adhere to the guidelines put in place to protect consumers. Furthermore, educating yourself regarding the approved usage of certified colors and flavors for your lip cosmetics will lessen the risk of producing misbranded cosmetics.