Undecylenic Acid Explained Plainly
Undecylenic Acid is the headline ingredient in Nail Defender. Here is what it actually is, and is not, in this product.
What it is
Undecylenic Acid is a fatty acid long used in topical skin-care formulas. It also appears in some FDA OTC-monograph antifungal drug products, where it must be used at disclosed concentrations, commonly 10% to 25%.
Why the Drug Facts label matters
An actual OTC antifungal drug carries a Drug Facts label listing the active ingredient, its percentage, and approved uses. Nail Defender's materials show no such label and no stated percentage.
What that means for buyers
Without that disclosure, we cannot confirm Nail Defender is formulated or regulated as an OTC antifungal drug. We treat it here as a named cosmetic ingredient, not a confirmed drug-strength active.
Our position
We do not repeat marketing claims that this spray eliminates nail fungus. See the ingredients page and what counts as a drug claim.
