Home Ingredients 10-Undecenoic Acid (Undecylenic Acid)
Anti-InflammatoryHair, Skin & NailsGut Health

10-Undecenoic Acid (Undecylenic Acid)

Evidence Level
Limited
2 Clinical Trials
4 Documented Benefits
2/5 Evidence Score

10-Undecenoic acid (also called undecylenic acid) is an 11-carbon unsaturated medium-chain fatty acid produced industrially from castor oil. It is best known as an FDA-approved over-the-counter topical antifungal — included in Category I of the OTC monograph for athlete's foot, jock itch, and other dermatophyte infections. By contrast, oral undecylenic acid as a dietary supplement (often marketed for intestinal candida) sits in a very different evidence position: human clinical data are sparse, and most mechanistic support comes from in vitro antifungal work against Candida albicans biofilms and dermatophyte cultures. Oral use should be considered off-label-style and undertaken with clinician input, particularly for individuals with GI conditions or those on systemic antifungals.

Studied Dose Topical: per FDA OTC monograph (Category I). Oral: no FDA-recognized dose; capsules commonly 250-500 mg, 1-3 times daily.
Active Compound 10-Undecenoic acid (undecylenic acid) — an 11-carbon unsaturated medium-chain fatty acid; topical (FDA Category I OTC antifungal) and oral capsule forms.

Benefits

Topical antifungal support (FDA Cat I)

Undecylenic acid and its calcium salt are FDA Category I OTC antifungals for athlete's foot, jock itch, and ringworm, with regulatory recognition of their efficacy in these topical indications. This is the strongest evidence position for undecylenic acid.

Supported by Trial 1

Anti-Candida mechanism in laboratory studies

In vitro studies report that undecylenic acid inhibits hyphal transition and biofilm formation in Candida albicans, including activity against established biofilms — mechanistic support for the antifungal positioning, though direct human oral data on intestinal candida endpoints remains thin.

Supported by Trial 2

Adjunct to skin and nail care routines

Topical undecylenic acid formats fit into broader skin and nail hygiene routines for fungal-prone areas, and are commonly used alongside foot powders and moisture-management strategies for athlete's foot and similar conditions.

Supported by Trial 1

Medium-chain fatty-acid antimicrobial chemistry

Like other medium-chain fatty acids, undecylenic acid is thought to act in part through disruption of microbial membranes — a non-specific mechanism that contributes to broad antifungal activity in vitro and helps explain its long-standing topical use.

Supported by Trial 1, Trial 2

Mechanism of action

1

Inhibition of Candida hyphal transition and biofilm formation

In vitro studies show undecylenic acid suppresses the yeast-to-hyphal morphological switch in Candida albicans and inhibits biofilm formation and architecture — mechanistic targets considered relevant to candida pathogenicity in mucosal and skin settings.

2

Microbial membrane disruption

As a medium-chain unsaturated fatty acid, undecylenic acid partitions into microbial cell membranes and is thought to compromise membrane integrity in susceptible fungi, contributing to its broad antifungal activity in vitro and in topical clinical use.

3

pH-dependent antifungal activity

Antifungal activity of undecylenic acid is pH-dependent, with higher potency in more acidic conditions where the protonated (uncharged) acid form predominates and can cross fungal membranes. This pH-sensitivity is a long-recognized feature of undecylenic acid pharmacology.

Clinical trials

1
Undecylenic acid — FDA OTC antifungal monograph

FDA OTC monograph review of undecylenic acid and its calcium salt for athlete's foot, jock itch, and ringworm, placing both in Category I (generally recognized as safe and effective) for these topical indications. Summarized in monograph review.

Population evidence base — patients with topical dermatophyte infections; aggregated across multiple clinical and consumer-use sources.

Undecylenic acid retains FDA Cat I status as a topical antifungal for tinea pedis, tinea cruris, and tinea corporis. Regulatory recognition of effectiveness in these topical indications is the strongest evidence position for this fatty acid.

2
Undecylenic acid antifungal mechanism — in vitro studies

In vitro studies evaluating undecylenic acid effects on Candida albicans biofilms, hyphal transition, and virulence factor expression. Mechanism-focused, not clinical outcome trials.

Candida albicans cultures and biofilm models; mechanistic in vitro work.

Undecylenic acid suppressed hyphal transition, biofilm formation, and virulence factor expression in Candida albicans cultures. Mechanistic support for antifungal positioning; oral human clinical outcome trials for intestinal candida endpoints remain limited.

Side effects and drug interactions

Common Potential side effects

Topical: occasional skin irritation, redness, or burning at application site.
Oral: GI symptoms (nausea, heartburn, loose stools) are commonly reported in clinical practice with oral capsules; clinical safety data are limited.
Theoretical Herxheimer-like reactions sometimes reported anecdotally with oral antifungal regimens.
Avoid contact with eyes and broken or weeping skin for topical use.
Discontinue and seek clinician evaluation if rash worsens or oral use causes persistent GI symptoms.

Important Drug interactions

Topical antifungals — generally compatible; avoid layering multiple irritating topicals on the same area.
Systemic azole antifungals (fluconazole, itraconazole) — coordinate use with prescribing clinician; theoretical additive antifungal effect.
Oral hepatotoxic medications — limited interaction data with oral undecylenic acid; consult clinician for high-dose oral regimens.
Probiotics — generally compatible; some clinicians stagger oral antifungal and probiotic dosing by several hours.

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Frequently asked questions about 10-Undecenoic Acid (Undecylenic Acid)

What is undecylenic acid used for?

Undecylenic acid (undecenoic acid) is a fatty acid with antifungal properties, used mainly topically for fungal skin infections like athlete's foot, jock itch, and ringworm, and sometimes internally for candida and yeast support.

Does undecylenic acid help with fungus?

Yes, it is an established topical antifungal (found in many over-the-counter athlete's-foot and jock-itch products) effective against common skin fungi. Internally, it is used in some candida protocols, though that evidence is more limited.

How is undecylenic acid used?

Topically it is applied to affected skin as directed in antifungal products; internally it is taken in capsules within candida-support protocols. Follow product labeling.

Is undecylenic acid safe?

Topical undecylenic acid is generally safe and well tolerated, with occasional mild skin irritation. Internal use is generally tolerated but less studied; those with medical conditions or on medication should check with a doctor. For persistent fungal infections, see a doctor.

What is 10-Undecenoic Acid?

10-Undecenoic acid (also called undecylenic acid) is an 11-carbon unsaturated medium-chain fatty acid produced industrially from castor oil. It is best known as an FDA-approved over-the-counter topical antifungal — included in Category I of the OTC monograph for athlete's foot, jock itch, and other dermatophyte infecti…

What is 10-Undecenoic Acid used for?

10-Undecenoic Acid is researched primarily for Anti-Inflammatory, Hair, Skin & Nails, and Gut Health. Undecylenic acid and its calcium salt are FDA Category I OTC antifungals for athlete's foot, jock itch, and ringworm, with regulatory recognition of their efficacy in these topical indications.

What is the recommended dosage of 10-Undecenoic Acid?

The clinically studied dose is Topical: per FDA OTC monograph (Category I). Oral: no FDA-recognized dose; capsules commonly 250-500 mg, 1-3 times daily. Always follow the product label and check with a healthcare provider for personal advice.

Is 10-Undecenoic Acid safe, and does it have side effects?

For most healthy adults, 10-Undecenoic Acid is well tolerated at studied doses. Reported effects can include: Topical: occasional skin irritation, redness, or burning at application site. Oral: GI symptoms (nausea, heartburn, loose stools) are commonly reported in clinical practice with oral capsules; clinical safety data are limited. It may also interact with some medications. 10-Undecenoic Acid is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does 10-Undecenoic Acid interact with any medications?

Possible interactions include: Topical antifungals — generally compatible; avoid layering multiple irritating topicals on the same area. Systemic azole antifungals (fluconazole, itraconazole) — coordinate use with prescribing clinician; theoretical additive antifungal effect. If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for 10-Undecenoic Acid?

NutraSmarts rates the evidence for 10-Undecenoic Acid as Limited (2 out of 5). It is backed by 2 clinical trials and 2 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(2 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. No authors listed. Undecylenic acid. Monograph. Altern Med Rev. 2002;7(1):68-70.PubMedUsed to support: Monograph summarizing undecylenic acid as a topical antifungal agent with use in candidiasis, dermatomycoses, herpes simplex, and stomatitis — concise overview of its OTC antifungal positioning and mechanism class.
  2. Shi D, Zhao Y, Yan H, et al. Antifungal effects of undecylenic acid on the biofilm formation of Candida albicans. Int J Clin Pharmacol Ther. 2016;54(5):343-53. doi: 10.5414/CP202460.PubMedUsed to support: In vitro study showing undecylenic acid inhibits Candida albicans biofilm formation and virulence factor expression — mechanistic support for the antifungal positioning of undecylenic acid against candida.