TUESDAY, Jan. 18 (HealthDay News) -- Natroba (spinosad) Topical Suspension 0.9 percent has been approved by the U.S. Food and Drug Administration to treat head lice in people aged 4 years and older.

Spread primarily by direct contact, head lice are not thought to cause disease, the FDA said in a news release. The parasitic insects feed on human blood, and live on the head, eyebrows and eyelashes.

Natroba is a topical medication designed to be applied to the scalp or hair. It should be used exactly as prescribed, the agency stressed.

In clinical testing, 552 people were given a 10-minute treatment with Natroba, and a second treatment was applied if live lice were observed 10 days later. After 14 days, about 86 percent of users were lice free, compared with 44 percent among study participants who didn't get the drug.

The most common side effects were irritation of the eyes and skin. The product contains benzyl alcohol, and is not recommended for use in children under the age of 4 years, the FDA said. Topically applied products containing benzyl alcohol have been associated with serious reactions in younger children, including death, the agency warned.

More information

To learn more about head lice, visit the U.S. Centers for Disease Control and Prevention.