Please note: Undecenoic acid is also known as 10-undecenoic acid, Undecylenic acid, and Undec-10-enoic acid.

The antifungal nature of undecenoic acid is known for a very long time. Since 1949, salts of undecenoic acids have been used by the food industry to inhibit yeasts and fungi and by the medical industry as antifungal drugs. It is present in its salt form in many over-the-counter topical antifungal medications. Yes, undecenoic acid is good for candida infections – but let us find out what exactly undecenoic acid is and how does it work as an anti-candida agent.

What is Undecenoic acid?

Undecenoic acid is also known as 10-undecenoic acid, Undecylenic acid, and Undec-10-enoic acid. PubChem, describes it as a naturally occurring fatty acid with antifungal properties. 10-Undecenoic acid is derived from castor bean oil. It is produced by cracking of castor-oil under pressure and is a foul smelling liquid.

10-undecenoic acid also occurs naturally in the body (in sweat) in small amounts. Therefore, one can imagine that it is not totally alien to the human system and that at least in small amounts the body can tolerate it well.

Medical Uses

Undecenoic acid can irritate the mucous membranes in some people. Therefore salts of this acid seem to be a reasonable alternative. That these salts have up to four times more antifungal activity compared to undecenoic acid and may have over 30 times more activity that caprylic acid as was shown in a study by the American scientists Peck and Rosenfeld in 1938.

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Undecenoic acid has been used in many topical antifungals to cure athlete’s foot and toenail fungal infections. Undecenoic acid and its salts were used to treat fungal infections of the foot (tinea pedis) in several studies conducted during World War II. These were the first agents that could cure tinea pedis without causing much irritation or side effects.

In 1980, Chretian and colleagues from USA conducted a controlled double blind clinical trial on the use of zinc salt of this fatty acid in powder form in curing tinea pedis. They found that 88% patients treated with this powder had negative culture results in 4 weeks as compared to only 17% patients in the control group.

The topical OTC products can be in the form of ointments, powders and liquids. Zinc salt of undecylenic acid is widely used in these preparations as free undecylenic acid is irritating to skin and mucous membranes. Zinc salts of this compound make it non-irritating.

Can undecenoic acid really kill candida?

As we learned above, undecenoic acid has historically been used to treat fungal infections of skin, especially the feet. What about candida? Is there any scientific basis supporting the use of undecenoic acid for candida infections? Let’s have a look.

In 1939, Hoffman, Schweitzer and Dalby from USA showed that fatty acids containing 8 to 12 carbon atoms were most effective against fungi – undecenoic acid has 11 carbon atoms. In 1945, Shapiro and Rothman also from USA studied the effect of zinc salt of undecenoic acid on 150 patients with skin fungal infections and found it to be effective against a range of fungi including candida. The first study that proved the antifungal nature of undecenoic acid was itself done on candida. Undecenoic acid has been used since then, in various forms, to treat fungal infections of the skin.

Undecenoic acid stops conversion of candida to pathogenic form: Another common commercial usage is in denture liners. Dentures are often found to be colonized by candida and denture liners are used to treat denture stomatitis which is caused by candida. McLain and colleagues from USA in 2000 studied denture liners coated with or without undecenoic acid. They found that those that were coated with undecenoic acid inhibited the growth of candida. These scientists also found that undecenoic acid did this by not allowing it to convert from the yeast to the pathogenic hyphal (filamentous) form.

Undecenoic acid affects the cell surface of candida: Shi and colleagues from China treated Candida albicans cells with different concentrations of undecenoic acid and found that even at very low concentrations the cell surface of candida was affected. When observed under electron microscope the cells looked deformed with crumpled cell surface.

Undecenoic acid inhibits enzymes involved in candida pathogenesis: Shi and colleagues also found that the treatment also decreased the enzymatic activity of candida cells that allows candida to become pathogenic. The two main types of enzymes affected were the protein degrading enzymes and the fat degrading enzymes – both of which increase the virulence of candida.

Oral use of undecenoic acid

Considering its irritant effect on the mucous membranes, a valid question that arises when talking about undecenoic acid is whether it can be safely used in oral form? Is there any scientific literature to back up its oral use?

In 1949, Henry Harris Perlman, an M.D. from USA published the first report on its oral use. He experimented with oral dosages of undecenoic acid to treat psoriasis and neurodermatitis. He first tested it for toxicity on mice, rabbits and guniea-pigs and found it to be relatively non-toxic. He then put it into perles and capsules to treat children. He found higher doses of 6 to 15 grams per day to have some side effects like nausea, vomiting, and burning sensation in the stomach etc. He suggested use of enteric coating to prevent the side effects.

In 1952, Hopkins and Murphy presented their first record of use of undecenoic acid to treat systemic fungal infection of the lungs. The patient was given 10.5 grams orally every day for four months that took care of his infection.

As the side-effects of undecenoic acid are limited only to gastro-intestinal disturbance with no known major issues of toxicity as such, a sustained release dosage form is useful in reducing the gastro-intestinal side-effects. CanXida Remove is a sustained time-release formula that contains undecenoic acid along with other anti-candida components. This ensures that undecenoic acid does not give you the gastrointestinal side effects. Additionally, CanXida Remove does not have just undecenoic acid as the active anti-candida component – there are several others as well! This means that the dosage of undecenoic acid is not too large.

Another issue with undecenoic acid is that it is active only under acidic conditions as was shown long back by Herbert N. Prince from USA in 1959. What this means is that it will be very active in the stomach where the conditions are acidic (unless you use strong proton pump inhibiting antacids like zantac or omeprazole, or have low stomach acid issues) – but when it comes to intestines where the conditions are alkaline, it will get inactivated. To overcome this issue, anti-candida products like CanXida Remove that contain undecenoic acid also include betain HCL which provides acidic conditions to the undecenoic acid. When this is combined with a sustained time release formula, it ensures that active undecenoic acid reaches the intestines and has its effect there. Additionally, Prince also showed that the salts of undecenoic acid are more susceptible to inactivation by alkaline conditions than is free undecenoic acid itself. Thus, free undecenoic acid is more useful as an oral antifungal agent.

Undecenoic acid vs caprylic acid – what is the difference?

The following table outlines the differences and similarities between undecenoic acid and caprylic acid. The differences highlight the fact that a combination of these two would achieve more anti-candida activity compared to each of these by themselves.

	Undecenoic acid	Caprylic acid
Other names	10-undecenoic acid, Undecylenic acid, and Undec-10-enoic acid	Octanoic acid, N-octanoic acid, Octylic acid, N-caprylic acid, N-octylic acid
Source	Castor oil	Coconut oil, milk, palm oil
Chemistry	Medium chain (11 carbon), unsaturated fatty acid	Medium chain (8 carbon), saturated fatty acid
Natural or synthetic	Synthetic – prepared by cracking castor oil under high pressure	Occurs naturally in the food sources.
Form	Liquid	Liquid
Smell in pure form	Unpleasant, sweat-like	Unpleasant, rancid-like
Taste in pure form	Unpleasant	Tasteless
Irritant	Yes, skin and mucous membranes	Yes, skin and mucous membranes
Antifungal/anti-candida Activity	Active in acidic environment (pH 4.5 to 6) Higher anti-candida activity than caprylic acid	Active in acidic environment (pH 4.5 – 6)
Mechanism of anti-candida activity	Prevents conversion to pathogenic form; affects cell integrity by disrupting cell membrane; reduces virulence by affecting virulence enzymes	Integrates into the cell membrane and disrupts the integrity of the cell; inhibits both the pathogenic and non-pathogenic forms of candida
Antibacterial Activity	Lower anti-bacterial activity than caprylic acid (Reference)	More active on Gram positive than Gram negative bacteria

Which form of undecenoic acid is best – tablets, capsule, liquid or something else? What is the best dosage?

It is best to have undecenoic acid in powder form mixed with caprylic acid and betaine HCL. It is important to have these in a sustained-release formula for best activity and least side effects.

It is suggested in an article by Thorne research Inc, to take 450-750mg undecenoic acid daily in three oral doses – in powder form. Some people can tolerate this dose, while others still may have some side-effects. Although the side-effects are generally not serious and are more of a nuisance, of course you would like to minimize the nuisance.

The dosage can vary depending on the combination of different anti-candida components. It is better to have a mix of different natural antifungal agents at smaller concentration than a large dose of a single ingredient. This is where canXida Remove is useful – it contains a mix of several different natural antifungal ingredients at a concentration that minimizes the side-effects.

Of course, even with CanXida Remove, you should always start with a low dose and slowly increase it to suit your body type and your sensitivity. Always listen to your body.

Can it be used topically?

Yes, it can be used topically as zinc salts. Free acid (not in salt form) of undecenoic acid should not be used topically as it can cause irritation and burning.

What are some good food sources of this acid?

There are no known food sources of this acid.

Although this fatty acid is produced from castor oil (No, castor oil is not a food source), we cannot obtain undecenoic acid by simply consuming the oil as it needs complex chemical process at high pressures for its extraction. Castor oil is a laxative by itself – it induces bowel movement, cleans up the entire intestine and does not stay in your system for longer than a couple of hours as the laxative effect is rather fast – so any antifungal activity, if it exists at all, will not be available to use due to its fast exit from the system.

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Is it also helpful against parasites?

No, there are no studies to show that it could be helpful against parasites.

Is it okay to take 10-undecenoic acid during pregnancy?

There are no controlled studies on the effect of oral intake of undecenoic acid during pregnancy. So, it is best avoided during pregnancy.

I have heard it is good for nail fungus is that true?

There is not much evidence that supports the use of undecenoic acid in treating nail fungus. Although it is effective in fungal infections of skin, it has not been found to be very effective in treating fungal nail infections. This is because in fungal nail infection, the fungus establishes itself within or under the nail which makes it very difficult for any topical medication to get through the nail and kill the fungus.

What are some side-effects?

Side-effects of topical undecenoic acid can include itching and burning. There is one report of allergic contact dermatitis as a side-effect.

Side-effects of oral undecenoic acid are more common at large doses. As already discussed in the article, the side-effects can be nausea, vomiting, and a burning sensation in the stomach. There is a report of labrynthitis (inflammation of inner ear) caused when patients were given undecenoic acid and also were taking nicotinic acid. So it may be advisable to watch out for side-effects especially if you are a smoker.