Undecylenic Acid Is One of The Most Effective Antifungal Ingredients Out There—Here's Why

A fungal infection certainly isn't ideal, but it can happen to anyone. And when you're dealing with these types of skin issues—think ringworm, athlete's foot, jock itch—it's imperative to treat them with an ingredient that's going to work specifically to target the root of the issue (with the guidance of your dermatologist, of course). And in the world of antifungal ingredients, undecylenic acid is one of the most common and effective options out there. Ahead, New York City-based dermatologists Nava Greenfield and Morgan Rabach explain how it works, what it can do, and how to use it.

What Is Undecylenic Acid?

While some might think it's an acid like glycolic or salicylic acid, undecylenic acid is actually a fatty acid, an unsaturated one that's already naturally-found in the body. "It's used as an active ingredient or part of an active ingredient in many topical antifungal treatments," explains Rabach. (Fun fact: It's not just for topical use. It's also found in many oral supplements in order to increase good bacteria in the gut, she adds.)

Benefits of Undecylenic Acid for Skin

As mentioned, it's an antifungal, meaning it prevents and eliminates topical fungus that can grow on skin (often times on the feet and around the toes, or in areas like the groin and under the breasts) as well as the nails. But, how exactly does it do that? "Undecylenic acid works by preventing candida albicans, a yeast that can live on the skin, from morphing into fungus," explains Rabach. It may also have fungicidal activity, which means that not only does it stop the fungus from growing, but that it can actually kill the fungus as well, adds Greenfield.

Side Effects of Undecylenic Acid

Minor redness and irritation may occur and is normal, says Rabach. But if it persists and is accompanied by swelling and/or pain, discontinue using the ingredient, she adds. Greenfield points out that having an actual allergy to the ingredient is also possible.

How to Use It

Like with so many other things, how often you use it ultimately depends on both the particular product you're using and the concentration of undecylenic acid it contains. Your best bet is to always follow directions for any specific product (more on that point in a moment). That being said, as a general rule of thumb, undecylenic acid, can usually be applied twice daily, particularly when it's in a cream formulation, says Greenfield. It should always go on clean, dry skin.

Also worth noting: While the ingredient can work against fungus on both the skin and nails, look at the product you choose carefully. "Many are marketed as 'skin' and 'nail area' fungus treatments, but will only mention in the fine print that they're ineffective in treating fungus on the actual nail in the fine print," says Rabach. "Make sure you read the instructions to ensure you're using your products correctly and that they are effective in treating your condition," she adds. In other words, choose any undecylenic acid product based on the particular area of fungus you're trying to treat.

No matter where you're using it, remember that many times a prescription-strength product is needed to treat these types of fungal infections, says Greenfield. Go ahead and try an over-the-counter version, for sure, but don't be discouraged or concerned if it doesn't get the job done.