Salicylic acid is a beta-hydroxy acid that is commonly used in skin care products, particularly anti-aging and acne treatments.
Salicylic acid is the most commonly used beta hydroxy acid (BHA) in cosmetics and skin care products. In chemistry, a BHA is an organic compound made up of a carboxylic acid functional group (-COOH) and a hydroxyl functional group (-OH) separated by two carbon atoms. With salicylic acid, both the hydroxyl and carboxylic acid groups are attached directly to an aromatic benzene ring, rather than along a linear carbon chain.
Salicylic acid can be obtained from the bark of willow trees. In the early 1800s, the active extract of the bark, called salicin after the Latin name for the white willow (Salix alba) was first isolated. Italian chemist Raffaele Piria discovered how to convert the substance into a sugar and a second component, which on oxidation becomes salicylic acid.
Salicylic acid is well known for its ability to treat acne, which is why it is found in many over-the-counter (OTC) acne products. In order to understand how salicylic acid treats acne, let’s first discuss what causes acne.
The first step in the formation of a blemish involves sebum, a naturally occurring oily substance that moisturizes, lubricates, and protects the skin and hair. While sebum production is a normal process, too much sebum can lead to clogged pores. The next step in the development of acne is triggered when follicles in the skin are not exfoliating properly. This means that keratin (a protein found within the skin) and sebum clog the follicle. When the follicle becomes clogged, a species of bacteria called Propionibacterium acnes accumulate and multiply in the follicle. The follicle becomes inflamed, thus leading to pimple formation.
Considering how acne develops, an effective treatment should work to balance the skin’s sebum levels, destroy the P. acnes bacteria, and reduce inflammation. Salicylic acid accomplishes all three of these actions.
Salicylic acid works well to balance sebum levels because it is lipid soluble. So rather than remaining on the surface of skin, salicylic acid penetrates deep into sebum-filled pores. It then exfoliates the pore lining, which loosens clogged dirt and oil and helps to wash these impurities away. Another way salicylic acid helps to fight acne is through its antibacterial activity. Salicylic acid has the ability to inhibit the production of various aspects necessary for binary fission (bacterial reproduction), such as fibrinogen, fibronectin, and alpha-hemolysis. Therefore, salicylic acid can neutralize the bacteria P. Acnes that is present in acne papules. Lastly, salicylic acid possess anti-inflammatory properties, which is ideal for treating acne since inflammation will worsen breakouts.
In addition to functioning as an acne treatment, salicylic acid is used in anti-aging skin care products due to its ability to brighten the complexion. It functions as an exfoliant by softening and dissolving keratin, thus allowing dead skin cells to shed naturally. Dendy Engelman, MD, of Manhattan Dermatology and Cosmetic Surgery, explains to Refinery29, “The exfoliative properties of salicylic acid have been shown to diminish the appearance of fine lines and wrinkles by promoting collagen growth.” Over time, exfoliation helps to reduce the thickness of the layer of dead skin cells, giving the skin a brighter, more glowing appearance.
Salicylic acid is approved by the US Food and Drug Administration (FDA) for use in OTC drug products. In addition to being FDA approved as a safe and effective acne drug product, it is also approved for use in OTC drugs for corn, callus and wart removal, as well as in anti-dandruff drug products.
Well-documented side effects of products containing salicylic acid include stinging, burning, dryness, peeling, and flaking of the skin. If you have sensitive skin, you should use products with salicylic acid with caution. According to the Mayo Clinic, people using products containing salicylic acid should not apply the following on the same area: abrasive soaps or cleansers, alcohol-containing preparations, benzoyl peroxide, resorcinol, sulfur, tretinoin, cosmetics or soaps that dry the skin, medicated cosmetics, other topical medicine for the skin.
Due to its exfoliative properties, salicylic acid can make the skin more sensitive to sunlight. For this reason, the FDA recommends using a sunscreen containing SPF 30 or more in conjunction with any product containing salicylic acid.
References: Wikipedia, “Salicylic Acid”, Wikipedia, “Beta hydroxy acid”, Indian J Dermatol. 2011 Jan-Feb; 56(1): 7–13, Science of Acne, “Sebum”, 2018, The Skincare Edit, “Why Salicylic Acid Is the Best Acid for Your Skin”, 2017, Refinery29, “We’ve All Been Underestimating This Acne-Fighter”, 2016, FutureDerm, “The Differences between Glycolic Acid, Salicylic Acid, Lipohydroxy Acid, and Gluconolactone”, 2014, Cosmetics Info, “Salicylic Acid”, Truth In Aging, “Salicylic Acid”, Mayo Clinic, “Salicylic Acid (Topical Route)”.