Tony Cenicola/The New York Times

More than a third of American adults use some form of complementary or alternative medicine, according to a government report. Natural remedies have an obvious appeal, but how do you know which ones to choose and whether the claims are backed by science? In this occasional series, Anahad O’Connor, the New York Times “Really?” columnist, explores the claims and the science behind alternative remedies that you may want to consider for your family medicine cabinet.

The Remedy: Tea tree oil.

The Claim: It fights acne.

The Science: Acne can be one of the most embarrassing and stressful skin conditions for both teenagers and adults.

Most over-the-counter creams and gels for the condition employ benzoyl peroxide, a compound developed decades ago that helps slough off dead skin cells and reduce inflammation. Benzoyl peroxide works for many people, but for those who find it ineffective or want an alternative, some experts recommend tea tree oil. The pleasant-smelling essential oil is extracted from the leaves of a tree native to Australia, Melaleuca alternifolia, and has been shown to have both antibacterial and cosmetic properties.

A small number of studies have found it particularly effective against mild to moderate acne. One study carried out by researchers at Royal Prince Alfred Hospital in Australia, for example, involved 124 acne patients. Some were assigned to apply a 5 percent tea tree oil treatment daily, and others used a 5 percent benzoyl peroxide solution. Both treatments, the researchers found, “had a significant effect in ameliorating the patients’ acne by reducing the number of inflamed and noninflamed lesions.” The tea tree oil worked more slowly than the benzoyl peroxide, they concluded, but it also produced fewer side effects.

A smaller, randomized study published in 2007 involved 60 patients with mild to moderate cases of acne. The patients were randomly divided into two groups, one treated with a gel containing 5 percent tea tree oil and the other given placebo for 45 days. The scientists found the tea tree oil worked far better than placebo in reducing the number and severity of acne lesions. And a study published in The British Journal of Dermatology in 2002 involving 27 subjects reached a similar conclusion on tea tree oil’s anti-inflammatory effects.

The Risks: Tea tree oil should be used only topically because it can have severe side effects if swallowed. It is generally safe when applied to the skin in moderate amounts, but according to the Mayo Clinic, some people may develop allergic rash, blistering or itching. People with eczema and other sensitive skin conditions should be particularly cautious.