The secret ingredient in a treatment for head lice is actually an over-the-counter skin cleanser, a U.S. researcher has revealed.

Dermatologist Dale Pearlman published a study in the journal Pediatrics last year suggesting his product, Nuvo lotion, was a non-toxic way to treat head lice. The study said the product was 96 per cent effective after three treatments with a 94 per cent long-term cure rate.

Pearlman described the product as a "dry-on suffocation-based pediculicide" that was only available from his office in California. Parents paid $285 US for the treatment, which has not been evaluated or approved by the U.S. Food and Drug Administration.

Checking for lice.

"In order to make this treatment available to individual practitioners to try, I now announce that the lotion I used in my research ... was actually Cetaphil cleanser," Pearlman said in a letter published in the Dec. 5 issue of Pediatrics.

The dermatologist said he tried to get drug companies to market his product so he could make money, but they turned him down.

Studies normally reveal enough about an experimental technique to allow other researchers to test the methods but Pearlman's secret made it impossible until now.

Pearlman called the patented treatment novel because it uses Cetaphil, a soapless cleanser, in a new way.

Cetaphil is applied to dry hair and scalp, distributed evenly with a comb and then blow dried in place to suffocate the lice.

The product is left in the hair for at least eight hours, and then washed out.

The Nuvo method offers "reliable treatment and accurate diagnosis," with an optional lice-identification test, Pearlman's website says. Other doctors said there's little harm in trying the remedy.

Sa'ar Shalev, 13, of Toronto tried it after his mother wanted to avoid pharmaceutical products for lice.

"I left it on overnight and I woke up and I washed it out," said Sa'ar. "So far I haven't had an itch since then." He needs to repeat the treatment in a week.

Galderma Laboratories, the makers of Cetaphil, said they had no data confirming or denying the product works against head lice. A bottle costs about $13.

Pearlman said his research was independent, without any financial or other association with Galderma.