Undecylenic Acid (Topical)

Undecylenic acid is an antifungal drug that is available both as a topical preparation and in oral capsules and tablets.


Undecylenic acid is an unsaturated fatty acid. It is derived through a chemical process from castor bean oil. This medication has been on the market for many years and is the active ingredient in many well-known over the counter products including Desenex and Cruex. Its primary use is as a topical antifungal preparation. Undecylenic acid treats a wide variety of different fungal species. Often, it is used in a topical solution and used to treat fungal infections of the nails. This medication in all of its forms is available without a prescription.

In recent years, undecylenic acid has been prepared in an oral form and used to treat a variety of fungal infections. At this time, oral undecylenic acid is not FDA approved to treat any illnesses. However, several studies are ongoing pointing to the possible efficacy of the drug in treating some types of fungal conditions as well as some other dermatological problems.

There are many newer medications on the market that treat the same type of fungal infections that undecylenic acid is indicated for. Many of the newer products need to be used for a shorter period of time. However, this drug is still very effective against many common fungal infections.

Conditions Treated

Undecylenic acid (topical) treats the following fungal infections:

Type of Medicine

  • Antifungal

Side Effects

The side effects for topical undecylenic acid are usually confined to the skin. However, there have been reports of more generalized allergic reactions in some patients who have used the topical form of this medication. These reactions include swelling of the face and lips and difficulty in breathing. These type of reactions are very rare when using the topical form of the medication.

The main side effect of topical undecylenic acid is burning and stinging at the application site. Sometimes, this type of side effect will be limited to the first day that the drug is used, and it will not necessitate that the use of the drug be discontinued.

Redness and rash around the application area have also been reported. This is often the result of prolonged usage of the medication. If redness, swelling or rash does develop, the patient should discontinue use of the drug and consult with a healthcare professional as soon as possible.

A limited number of patients will experience dryness and peeling during, or immediately after, the treatment period. If this is extensive, it needs to be reported to a physician.

Side effects have also been reported in those using the oral form of undecylenic acid. There have been reports of generalized allergic reactions with the oral form that include swelling of the face and difficulty breathing. These side effects are rare.

The major side effects reported by those using the oral form of undecylenic acid are associated with the gastrointestinal system. Patients using the drug have reported nausea, vomiting, and diarrhea.


The dosage of undecylenic acid is dependent on the condition that is being treated. For athlete's foot, if the cream is being used, a thin layer of the cream needs to be placed over the affected area twice a day after the affected area is thoroughly washed and dried. Treatment for athlete's foot should continue for at least four weeks.

When the powder or spray powder form of the product is used, enough of the product should be used to cover the area. These products also need to be applied twice a day to the affected area for a period of four weeks.

For ringworm infections, undecylenic acid topical products need to be applied for a minimum of four weeks. The area affected should be cleaned and dried.

Jock itch infections will have a different treatment period. The topical product needs to be applied in and around the affected area of the groin twice a day for a period of two weeks. Especially virulent cases may need to be treated for an additional two weeks. The area should always be cleaned and dried before the medication is applied.

Undecylenic acid in a solution is often used to treat fungal infections of the nail. Normally, an applicator brush is supplied. The patient should apply the solution with the brush to the affected nail or nails twice a day. This should continue until the patient sees clear nail growth begin to show. This may take six months.

Oral undecylenic acid is being used to treat some conditions. Patients should take between 450 and 750 mg of the oral medication per day divided into three separate doses. Oral undecylenic acid is not FDA approved, so there is not a set dosage pattern or recommendation.

As with all medications, the patient should use this medication for the duration of the recommended treatment period. If treatment is stopped too soon, it is likely that the fungal infection will reappear, and it will be more difficult to treat using the same medication.


When using topical undecylenic acid products to treat fungal infections, the patient should not at the same time use another type of medication used to treat fungal infections. There are many different types of antifungal medications that are now available over the counter. They have multiple effective ingredients. Only one topical antifungal product should be used at a time. If two preparations are used, it greatly increases the chance that the skin will become irritated. This may lead to blistering of the skin and possible skin infections.

There are no known drug interactions with the oral form of undecylenic acid. Those who are in poor health or who are taking prescription medications may wish to consult with a doctor or pharmacist before taking the oral form of undecylenic acid.


When using topical undecylenic acid, the patient needs to thoroughly wash his or her hands after using the medication. Fungal infections are easily spread to other areas of the body.

While topical undecylenic acid is useful for the treatment of ringworm on the body, topical undecylenic acid is not useful for the treatment of ringworm of the scalp. This type of infection is normally treated with oral products that must be obtained with a prescription.

Undecylenic acid is not recommended for use in patients that are under two years of age. Patients who are over the age of 70 may have more pronounced reactions to the drug, so caution is recommended when geriatric patients are using this medication.

Patients need to be aware that the oral form of undecylenic acid is not approved by the Food and Drug Administration for the treatment of any disease. It has undergone some limited testing. At the current time, the oral form is being marketed as a form of alternative medical treatment. There has been no testing as to whether or not the oral form is safe for children or older patients. No testing has been done on patients who are pregnant or nursing. Those with underlying conditions should consult a physician before using the oral form of this medication.


All forms of topical undecylenic acid need to be stored in a dry place at room temperature. They should not be refrigerated.

Oral undecylenic products should be stored in their bottle away from children. They should be stored at room temperature away from direct sunlight.


Undecylenic acid in its topical form is an antifungal medication that is available without a prescription. This drug has been used for many years. It is effective in treating a wide variety of topical fungal infections including athlete's foot, body ringworm, jock itch and yeast infections.

An oral form of undecylenic acid is now available over the counter. These products are not FDA approved, but they are used for treating fungal and non-fungal skin conditions as well as gastrointestinal fungal infections. Only limited testing has been done to determine if this form of the drug is truly effective.

The side effects of undecylenic acid topical are rare and usually mild. The most common side effects are skin irritation and redness. These side effects may go away during continued use of the medication.

Undecylenic acid products should not be used in children under the age of two. All oral forms of this medication should be used with caution as they are untested.

Those undergoing treatment with this medication need to be sure to continue their treatment for the entire treatment period in order to make sure that the fungal infection does not return in a more virulent form.