Insecticide-resistant lice are spreading across the world.
Patients and their caregivers are hesitant to apply toxic insecticides to their bodies and instead want lice treatments with nontoxic mechanisms of action.
The insecticidal pediculicide lindane is a known carcinogen that causes seizures in susceptible individuals. It’s also banned by the US Environmental Protection Agency for agricultural use. Meanwhile, the safer Chrysanthemum-derived pyrethrin insecticide class is allergenic and subject to resistance formation.
Now, new comparative study results show mineral oil pediculicides are noninferior to insecticide-based products.
Mineral oil clogs the respiratory spiracles and dissolves the shells of adult lice and nits. It’s a common nontoxic ingredient in a multitude of cosmetic and therapeutic skin products.
In the study, blinded researchers randomized patients with confirmed head lice to receive mineral oil shampoo or a pyrethroid-based pediculicide product. Notably, the differing products’ appearance and directions of use prevented patient blinding.
The patients applied the products twice daily 7 days apart, and the researchers inspected them 1 hour and 24 hours after the first application, before and after the second treatment, and on day 10.
By day 10, the mineral oil and insecticidal pediculicides cured 98% and 94% of patients, respectively. The mineral oil product also cured 90% of patients within 24 hours and reduced the magnitude of living lice in uncured patients. Meanwhile, the pyrethrin products had an 80% 24-hour cure rate. A single application of mineral oil was also more effective than a single dose of pyrethrin (78% vs. 60%).
Mineral oil patients reported easy residue removal from hair and “pleasant scalp” (moisturizing properties). On the other hand, the pyrethrin products produced a mild burning sensation and redness at application site more often than the mineral oil product.
Lice reinfested in a few patients in each group during the study period, which underscores the need for eradication technique counseling. To prevent reinfestation, patients should:
Mineral oil is not only well-tolerated and noninferior to pyrethrin products, but also retains efficacy in highly treatment-resistant lice populations and doesn’t promote resistance development. Additionally, mineral oil is safer than lindane, which is sometimes used after pyrethrin therapy failure.
Wolf L, et al. Efficacy and safety of a mineral oil-based head lice shampoo: a randomized, controlled, investigator-blinded, comparative study. PLOS One. 2016 Jun;11(6):e0156853.