Menthol

What is menthol?

Menthol is an organic compound found naturally in peppermint and other mint oils and also made synthetically. Applied to the skin, it produces a cooling sensation, which is why it appears in chest rubs, muscle rubs, anti-itch creams, lip balms and cough drops. In topical nail and foot products, menthol is often paired with camphor, another aromatic compound with a cooling, slightly numbing feel.

What the research says

Interest in menthol for nail fungus comes mainly from popular advice to apply mentholated chest rub to infected toenails. A small study tested this idea: 18 people with toenail fungus applied Vicks VapoRub, whose ingredients include menthol and camphor, for 48 weeks. Fifteen (83%) showed some positive effect, 5 (27.8%) had both laboratory and clinical cure, 10 (55.6%) had partial clearing and 3 showed no change (Derby et al., 2011). The study had no control group, so it is impossible to know how much of the change was due to the product, and it tested a full ointment rather than menthol alone.

The American Academy of Dermatology says that small studies of tea tree oil and mentholated cough-suppressing ointments suggest there may be some benefit, but that we still do not know how effective they are or what side effects could occur, and that larger studies are needed (AAD). We found no controlled trials of menthol by itself for nail fungus. Menthol’s best-established effect is sensory: it activates cold-sensing nerve endings, which is why products containing it feel cool and can temporarily distract from itching or minor aches. That sensation should not be mistaken for a sign that an infection is clearing.

How it’s used in products

Menthol is used in over-the-counter topical pain relievers, chest rubs, cooling lotions, oral care products and some nail and foot oils, often as a secondary ingredient for its cooling feel and scent. Nail oils rarely disclose its concentration.

Topical menthol is generally well tolerated at low concentrations, but it can cause skin irritation, burning or allergic reactions, especially on broken skin or under tight coverings. Do not apply heat over menthol products, keep them away from the eyes and mucous membranes, and stop if redness or blistering occurs. Products that combine menthol with camphor must be kept away from children, because camphor can be dangerous if swallowed. People with diabetes or poor circulation should have foot and nail problems checked by a clinician rather than relying on home remedies.