Medically reviewed by Michele Emery, DNP
Written by Our Editorial Team
Last updated 4/17/2020
Used to treat everything from acne to dandruff, salicylic acid is an ingredient that’s commonly found in shampoos, conditioners and other hair products.
In fact, it’s one of several important anti-dandruff and anti-hair loss ingredients included in our hair thickening shampoo.
Salicylic acid performs multiple functions at once on the skin and hair follicles. It can prevent sebum buildup, reducing the risk of acne developing on your face and scalp. It’s also proven to reduce the formation of dandruff, keeping your scalp free of dead, flaky skin.
In this guide, we’ll look at what salicylic acid does and how it works, complete with several scientific studies that look at how salicylic acid interacts with your skin and hair follicles.
Salicylic acid is a widely used medicinal ingredient that’s used as a treatment for everything from warts and calluses to dandruff, acne, ringworm and a variety of other skin conditions.
Found naturally in certain foods, salicylic acid was originally sourced from salix alba, or white willow bark, and myrtle.
Salicylic acid works by safely and effectively stripping away the epidermis, or external layer of skin. By gently removing the outermost layer of skin, salicylic acid helps prevent skin conditions like pimples, fungal infections and dandruff from developing over time.
Generally safe and widely used, salicylic acid is listed on the WHO List of Essential Medicines as one of the most important medicinal ingredients in the world.
When used topically in a shampoo, salicylic acid naturally strips away the outermost layer of the epidermis, allowing dead skin to wash off your scalp when you shampoo and condition your hair.
From dandruff to uncomfortable, itchy hair, many of the most common scalp conditions worsen when dead skin is allowed to build up on your scalp. You can think of salicylic acid as a tool for loosening dead, irritated skin, making it easier to wash away when you shower.
The unique chemical properties of salicylic acid make it one of the most effective ingredients for penetrating the scalp and cleansing your skin.
Unlike most shampoo ingredients, salicylic acid can enter into and cleanse pores, preventing oil buildup and helping to unclog your hair follicles. This can mean healthier hair growth and fewer skin issues, such as seborrheic dermatitis or dandruff.
For example, a 1987 study found that people treated with shampoo containing a mix of salicylic acid and sulfur had a noticeable reduction in the amount of skin scaling (dry, flaky skin) on their scalps.
Simply put, if you’ve noticed dandruff or scalp itching caused by dry skin, salicylic acid is worth considering as an addition to your hair care protocol.
While salicylic acid isn’t directly linked to a reduction in hair loss (like minoxidil or finasteride), it can potentially play a role in helping you keep more of your hair.
This is because salicylic acid is vital for washing away excess sebum — a waxy, oily substance that can contain dihydrotestosterone, or DHT, the key androgenic hormone responsible for hair loss in men.
Currently, there isn’t any conclusive scientific evidence showing that excess DHT contained in scalp sebum can contribute to male pattern baldness. However, washing away sebum is ideal for keeping your scalp healthy and free of acne, irritation or dandruff in the first place.
In short, should you view salicylic acid as a miracle cure for baldness? No. However, it offers a variety of proven benefits for scalp and hair health, as well as the potential to lower DHT levels on your scalp by keeping your skin fresh, clean and free of excess dandruff and sebum.
Several studies have been conducted on salicylic acid’s potential as a hair treatment. One, from 2002, compared salicylic acid to Nizoral® shampoo — a popular anti-dandruff shampoo — to see which was the most effective treatment for dandruff and seborrheic dermatitis.
The study found that both products significantly improved seborrheic dermatitis and reduced the amount of dandruff on the scalp. However, people treated with the salicylic acid shampoo had a larger improvement in itching symptoms caused by seborrheic dermatitis.
Another study from 2009 showed that a shampoo containing salicylic acid produced significant improvements in skin redness, itching, discomfort and dryness caused by seborrheic dermatitis.
This study used two blends of salicylic acid — one mix of salicylic acid with lipohydroxy acid, and one of salicylic acid with ciclopirox olamine and menthol. Both formulas produced a measurable, significant improvement, with only a small difference between each group.
In short, salicylic acid works very well for treating dandruff and the skin symptoms of seborrheic dermatitis. This is verified by numerous scientific studies. While it may also help in treating hair loss, there isn’t any scientific data to prove this just yet.
Salicylic acid is viewed as a safe and effective ingredient for treating dry skin and scalp conditions like dandruff or seborrheic dermatitis.
The most frequently reported side effect is skin irritation, although this is rare and usually very mild. Any persistent or serious side effects when using salicylic acid should be discussed with your healthcare provider immediately.
Most of the time, salicylic acid is used in relatively small quantities as part of a hair health and dandruff prevention shampoo. Use it as frequently as you would a normal shampoo to free up and wash away excess skin sebum to keep your hair and scalp in optimal condition.
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