Undecenoic Acid
Is It Right for You?
A complete guide to Undecenoic Acid — what it treats, how it works, dosages, side effects, and when a clinician may prescribe it following an online consultation.
What Is Undecenoic Acid?
Undecenoic acid (undecylenic acid) is a topical antifungal used to treat fungal skin infections such as athlete's foot. It helps clear the infection and ease the itching, scaling, and discomfort it causes.
It is available in creams, ointments, powders, and sprays, sometimes combined with zinc undecenoate, which adds a soothing, astringent effect. Many products are available from pharmacies, with some on prescription.
Some undecenoic acid products are available to buy, while certain preparations are prescription-only in the UK. A licensed clinician can review your skin through a telehealth consultation and prescribe where appropriate.
What Conditions Is Undecenoic Acid Used For?
Undecenoic acid is used for:
treating the fungal infection between the toes and on the feet, easing itching and scaling.
treating ringworm-type infections on the body where appropriate.
the zinc-containing combination helps soothe and dry the skin, reducing irritation.
Fungal infections often return if treatment is stopped too soon. Continue using undecenoic acid for the full recommended time, usually for a period after the skin looks better, to fully clear the infection.
How Does Undecenoic Acid Work?
Undecenoic acid is a fatty acid with antifungal properties. It works by stopping the growth of the fungi (dermatophytes) that cause skin infections such as athlete's foot.
By inhibiting the fungus, it allows the infected skin to recover, reducing the itching, redness, and scaling associated with the infection.
When combined with zinc undecenoate, the zinc adds a soothing, mildly astringent and protective effect, helping to dry and calm the affected skin while the antifungal clears the infection.
Dosages & Administration
The correct dose depends on the type and severity of infection, age, weight, and kidney function. Always follow your clinician's instructions. The table below is for general reference only.
Administration Tips
Wash and dry the area well first, especially between the toes, then apply the product as directed and wash your hands afterwards.
Keep using it for the full course, including for a period after the skin looks normal, and keep feet clean, dry, and aired to prevent recurrence.
Side Effects of Undecenoic Acid
Undecenoic acid is generally well tolerated. Side effects are local and uncommon.
- Mild skin irritation or stinging
- Redness at the application site
- Itching
- Dryness
- Severe irritation, blistering, or burning
- Signs of an allergic skin reaction (worsening rash, swelling)
- Spreading or worsening infection
- Severe allergic reaction
If your skin does not improve after the recommended period, worsens, or becomes more painful, weepy, or spreading, stop and seek advice. You may have a different or more severe infection needing other treatment.
Drug Interactions
Always disclose all prescription drugs, over-the-counter medicines, vitamins, and supplements to your clinician or pharmacist before starting undecenoic acid.
Other products on the same area can affect the result or cause irritation; space them as advised and avoid layering unnecessarily.
Tight, non-breathable shoes and damp socks encourage fungal growth and can reduce the benefit of treatment.
Using multiple antifungal products at once is rarely needed; follow your clinician's or pharmacist's advice.
Important Warnings
Keep applying undecenoic acid for the full recommended period, including after the skin looks better, to stop the infection returning.
Keep feet clean and dry, change socks regularly, and let shoes air. Treating footwear with an antifungal powder can help prevent reinfection.
Keep the product away from the eyes and broken skin, and avoid using it on areas it is not intended for unless advised.
Use only if needed and as directed. Tell your clinician if you are pregnant or breastfeeding so suitable advice can be given.
Speak to a Clinician About Treatment
Getting advice no longer means sitting in a waiting room. Through The GP Service, you can consult with a licensed clinician in minutes — from home, on your lunch break, or wherever works for you. If treatment is clinically appropriate, your clinician can issue a prescription during the consultation. A consultation does not guarantee a prescription.
The treatment you need, when you need it.
Undecenoic Acid FAQs
Some products are available to buy, while certain preparations are prescription-only. A licensed clinician can review your skin and prescribe where appropriate via telehealth.
Improvement often takes a couple of weeks, and you should keep applying it for a period after the skin looks normal to fully clear the infection and prevent recurrence.
Reinfection is common if feet stay damp or footwear is not treated. Good foot hygiene, dry socks, and aired shoes help, along with completing the full course.
Yes. Athlete's foot often starts between the toes, so apply it there as directed after drying the area well.
If your skin does not improve, worsens, or spreads, seek advice, as you may have a different infection or need a different treatment.
The zinc undecenoate adds a soothing, drying, and protective effect to the antifungal action, which can help calm irritated, sweaty skin.