What Is Salicylic Acid? What to Know About This Favorite Acne Treatment

You've probably heard of the skin-care ingredient salicylic acid, but you may not have a detailed understanding of what it does, what it's derived from, and how it compares to other acne fighters.

Commonly used in a myriad of formulations, salicylic acid is used for various conditions, from acne to warts and dandruff. It's gentle enough for daily use, but you have to be careful about what other ingredients you mix it with. It's a beta hydroxy acid (BHA) that gently exfoliates the skin. You can find salicylic-acid products in the form of toners, serums, cleansers, body washes, and even shampoos.

Keep reading for two skin-care experts' responses to the most common questions surrounding salicylic acid.

"Salicylic acid is an active ingredient that can be naturally derived from willowbark tree," Anita Sun, a medical aesthetician and founder of Dermovia, tells POPSUGAR. "It is a beta hydroxy acid (BHA) and is a gentle exfoliating ingredient that is also anti-inflammatory and antibacterial."

The aforementioned characteristics make salicylic acid a favorite among those with mature, oily, or acne-prone skin. "Salicylic acid is very beneficial for turning over dull skin to reveal brighter skin. It's effective in exfoliating away surface dead skin cells, and its sloughing benefit helps to reduce acne and prevent bacteria from spreading," Sun says. "BHAs are oil-soluble, so they can penetrate deeper into the skin to loosen and unclog oil sebum from pores."

Salicylic acid can effectively decrease oil production and sebum secretion, leaving you with a brighter, clearer, and more even complexion. "It works by loosening the cellular junctions of the stratum corneum, which is the outermost layer of the skin," Snehal Amin, MD, cofounder and surgical director of MDCS Dermatology, says.

But you have to be cautious about using high concentrations and quantities. When overdone, salicylic acid can cause excessive skin dryness, so save potent products for spot treatments and use masks and treatments with care.

Salicylic acid can treat a myriad of skin conditions besides acne, including warts, rosacea, scars, and rough-texture skin concerns like psoriasis. For acne, Dr. Amin says a low concentration of 0.5 to 10 percent is effective at dissolving sebum and reducing inflammation. "For conditions where there is excess keratin buildup such as psoriasis [and] keratosis pilaris, salicylic acid three to six percent is used," says Dr. Amin. "At higher concentrations, salicylic acid is used to treat warts, corns, and as a peeling agent."

Like with many skin-care ingredients, you have to be careful what you mix salicylic acid with. Niacinamide is OK to layer on the skin after salicylic acid because it's "a higher pH (basic) compound, which is complementary to salicylic acid," Dr. Amin says.

Combinations to avoid include astringents and other peeling agents. In general, "avoid combining salicylic acid with other products that may cause skin irritation or exfoliation."

Benzoyl peroxide and salicylic acid are both common acne treatments, but they're very different ingredients. Determining which ingredient would be best for you depends on the type of acne you're experiencing. Salicylic acid is good for fighting inflammatory breakouts, as well as preventing new pimples from forming. "Salicylic acid also acts as an anti-inflammatory ingredient, helping to decrease the redness and puffiness of acne blemishes," Ted Lain, MD, board-certified dermatologist and chief medical officer at Sanova Dermatology, previously told POPSUGAR. Benzoyl peroxide, on the other hand, attacks acne-causing bacteria to treat and prevent pimples.

If you're well-versed in skin care, you know retinol is a great ingredient for fighting premature signs of aging and even treating adult acne. You may find yourself wanting to incorporate the powerful ingredient into your routine but if you're already using salicylic acid, you should stick to using only one. "Retinol is extremely unstable," NYC-based dermatologist, Joshua Zeichner, MD, FAAD, previously told POPSUGAR. "It doesn't play nicely with a salicylic acid or benzoyl peroxide. Combining two leave-ons, like masks or overnight treatments, can hit the skin too hard if you use them all at one time."

You should be careful about using salicylic acid while pregnant. "Salicylic acid over-the-counter topical formulations (less than 2 percent concentration) are generally considered safe to use up to one to two times a day, per the American College of Obstetrics and Gynecology," Dr. Amin says. "No studies have specifically been conducted in pregnancy on topical salicylic-acid use. However, given the very small proportion [that's] absorbed through the skin, it is unlikely to pose any risk to the fetus."

That said, you should avoid high doses of topical salicylic acid while pregnant. "Salicylic acid chemical peels and higher concentration formulations used in doctor's offices should be avoided during pregnancy," he says. "At these higher concentrations, salicylic acid can be absorbed into the bloodstream, and effects are not known on the baby during pregnancy."