By definition, in organic chemistry, an alcohol is an organic compound with a hydroxyl (OH) functional group on an aliphatic (non-aromatic) carbon atom.
The “bad reputation” that alcohol has, when applied to cosmetics or topical skincare, refers to ‘denatured alcohol’ or ‘specially denatured’ (SD) alcohol—it has a drying effect on the skin which may be appreciated by those with oily skin. However, the effects are short-lived and there may be long-term negative consequences. When high concentrations of alcohol or SD alcohol are used in the formulation of skincare products, this ingredient can cause drying and irritation. It may also cause erosion of the skin’s surface layer, leading to a weakened skin barrier.
Other types of alcohol to know include Cetyl Alcohol, Searyl Alcohol and Cetearyl Alcohol. These are “good” ingredients, and in small amounts, are suitable for inclusion in skincare products as they enhance the texture and ‘feel’ of the product and help keep ingredients stable.
Propylene Glycol and Polypropylene Glycol fall into another category of alcohol. Both have the ability to attract water and function as a humectant, and are commonly found in moisturisers to enhance the appearance of skin by reducing flaking and restoring suppleness. Propylene Glycol is one of the most widely used ingredients in cosmetics and personal care products, where it is also used to lower the viscosity of products. It is used in many types of cosmetic formulations including facial cleansers, moisturisers, bath soaps, shampoos and conditioners, deodorants, shaving preparations, and fragrances, the list goes on. It is also used as an inactive ingredient in many oral and injectable drugs, and is safe enough that the US Food and Drug Administration (FDA) has allowed its use at levels as high as 98 per cent in topical drugs and 92 per cent in oral solutions! Other ingredients in this group include Butylene Glycol and Pentylene Glycol which have hygroscopic features or, in other words, they absorb water, retain it and improve the skin moisture.
Mention should also be made of a commonly used ingredient, which is ‘alcohol-related’—Polyethylene Glycols (PEGs). These are petroleum-based compounds that are widely used as thickeners, solvents, softeners, and moisture-carriers. PEGs are commonly used as cosmetic cream bases and have been deemed to be ‘GRAS’ (short for ‘Generally Regarded As Safe’) by the FDA.