ParaPRO: Innovations in Life Sciences

The Head Lice Life Cycle

Lice live for approximately 40 - 50 days and go through 3 stages in their life cycle:

Eggs: (also known as ova or nits) The female louse lays the egg with a waterproof, glue like substance that cements it to the hair shaft near the root. The eggs are about the size of a poppy seed and are difficult to see because their color easily blends in with the infested child's hair. They vary in color—from yellowish-brown to white. The eggs develop and hatch approximately 10 days later. Dandruff, sand and flakes of hairspray are commonly mistaken for eggs. Eggs (or egg casings) are not easily removed and must be carefully combed out with a fine-toothed comb. Hair, on average, grows about ½ inch per month. Lice will hatch in two weeks. So any eggs or nits that are found more than ¼ inch from the scalp have most likely hatched or are dead. Many schools have a "No Nit Policy," which means children who have had head lice are not readmitted to school until all the nits are gone.

Nymphs: Once the louse hatches, it is called a nymph and is barely visible to the naked eye. The nymph cannot reproduce because it is not fully developed. After about 12 days, it becomes an adult.

Adults: The adult louse can lay up to 4-10 eggs a day—starting another generation of lice. The adult stage lasts about 28 days. During their adult life, female head lice lay an average of 125 eggs.

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Ask your doctor if Natroba™ Topical Suspension is right for you or your child.

Natroba™ Topical Suspension is a pediculicide indicated for the topical treatment of head lice infestations in patients six (6) months of age and older.

Natroba™ Topical Suspension should be used in the context of an overall lice management program:
  • Wash (in hot water) or dry clean all recently worn clothing, hats, used bedding and towels
  • Wash personal care items such as combs, brushes, and hair clips in hot water
A fine-toothed comb or special nit comb may be used to remove dead lice and nits.

Natroba™ Topical Suspension contains benzyl alcohol and is not recommended for use in neonates and infants below the age of 6 months. Systemic exposure to benzyl alcohol has been associated with serious adverse reactions and death in neonates and low birth-weight infants. Most common adverse events were: application site redness (3%), eye redness (2%) and application site irritation (1%).

Consult the Patient Information, Full Prescribing Information and your doctor for more complete information on Natroba™ Topical Suspension.

You are encouraged to report negative side effects of prescription drugs to the FDA. Visit or call 1-800-FDA-1088.