What Is SD Alcohol?
SD alcohol 40 is a type of denatured alcohol used in cosmetics and skincare products. It is mainly used as an anti-foaming agent, astringent, antimicrobial agent, and a solvent.
SD alcohol, or “specially denatured” alcohol, is ethanol that contains a denaturant to make it taste unpleasant. This is done because ethanol is the same alcohol found in alcoholic beverages such as liquor, wine, and beer, and in the United States, alcoholic beverages are heavily taxed. In order to avoid paying beverage taxes on alcohol that is not meant to be consumed such as in skincare or cosmetics, the alcohol must be denatured per specific formulations given by the U.S. Government’s Alcohol and Tobacco Tax and Trade Bureau. The process adds a small amount of a denaturant to the alcohol to make it taste bad, thus creating alcohol that is not suitable for drinking but is otherwise similar for other purposes.
SD alcohol that is followed by a number on the ingredients list such as SD alcohol 40, is the designation given by the U.S. Bureau of Alcohol, Tobacco, and Firearms to the denaturing method used. Due to the diversity of industrial uses for denatured alcohol, hundreds of additives and denaturing methods have been used. Common denaturants in cosmetics and personal care products include denatonium benzoate, t-butyl alcohol, diethyl phthalate, and methyl alcohol. The process of denaturing alcohol does not chemically alter the ethanol molecule. In addition to SD alcohol 40, the specially denatured alcohols acceptable for use in cosmetics are SD Alcohol 23-A and SD Alcohol 40-B.
SD Alcohol 40
the good: SD alcohol 40 is mainly used to increase the longevity and stability of formulations by improving the texture and preventing the growth of bacteria.
the not so good: Alcohol can be a drying ingredient for some skin types.
Who is it for? All skin types except those that have an identified allergy to it.
Synergetic ingredients: Works well with most ingredients.
Keep an eye on: Can cause some irritation. If you have dry or sensitive skin you may want to avoid products with this ingredient.
Why Is SD Alcohol Used?
In cosmetics and skincare products, SD alcohol 40 has multiple functions, including as an anti-foaming agent, astringent, antimicrobial agent, and a solvent.
As an astringent, SD alcohol 40 causes the skin to contract. After topical application, astringents work on proteins called keratins, which function to hold skin cells together to form a barrier. The bonds between keratins are affected by temperature and pH, forming only when the skin is slightly acidic or cool. If the bonds break, the keratin molecules will separate, causing the outer layer of skin to swell. Astringents cool the skin and cause the bonds to reform. It is this process that produces the temporary toning effect associated with astringents.
SD alcohol 40 can often be found in soaps and hand sanitizers labeled as “antimicrobial” because it has strong bactericidal and fungicidal activity. The antimicrobial effects of alcohol are based on protein denaturation.
Lastly, SD alcohol 40 functions as a solvent to help other ingredients dissolve into a solution. This property of SD alcohol 40 also thins out formulations by compacting or shrinking the volume of the solution. Thinner formulations can help skincare products perform better since active ingredients have less volume to traverse to get to your skin.
Is SD Alcohol Safe?
The Cosmetic Ingredient Review Expert Panel, a group responsible for evaluating the safety of skincare and cosmetic ingredients reviewed the available data on SD alcohol 40. They concluded that safety of ingredients containing denatured alcohol, such as SD alcohol 40, should be based on the safety of the denaturants used since dermal application or inhalation of cosmetic products containing these ingredients will not produce significant systemic exposure to ethanol. The Panel considered that the adverse effects known to be associated with alcohol ingestion do not suggest a concern for SD Alcohols because of the presence of the denaturants. The safety of the alcohol denaturants Denatonium Benzoate, t-Butyl Alcohol, Diethyl Phthalate, and Methyl Alcohol was reviewed by the CIR Expert Panel in 2008 and found to be safe as used.
Despite the approval of SD alcohol 40 by the CIR Expert Panel, the safety of this ingredient in cosmetics and personal care products is controversial. When high concentrations of denatured alcohol are used in the formulation of skincare products, this ingredient can cause drying and irritation. Denatured alcohol can also cause erosion of the skin’s surface layer, leading to a weakened skin barrier. However, if lower concentrations of denatured alcohol are used, this ingredient may function solely as a degreasing agent, creating a better texture of the skincare formulation.
Ultimately, the safety of SD alcohol 40 in cosmetics and personal care products depends on both the type of denaturant and also the concentration that is used to create the formulation.
CIR, 2008. ‘Final Report of the Safety Assessment of Alcohol Denat., Including SD Alcohol 3-A, SD Alcohol 30, SD Alcohol 39, SD Alcohol 39-B, SD Alcohol 39-C, SD Alcohol 40, SD Alcohol 40-B, and SD Alcohol 40-C, and the Denaturants, Quassin, Brucine Sulfate/Brucine, and Denatonium Benzoate1’, International Journal of Toxicology.