Several classes of agents kill mites and lice, ranging from over-the-counter insecticides like permethrin to prescription options like spinosad and ivermectin. The best choice depends on which parasite you’re dealing with, where it is on the body, and whether resistance is a factor. Here’s what works, how well it works, and what to know before choosing.
Permethrin: The Most Common Starting Point
Permethrin is the most widely used agent for both lice and mites. For head lice, it’s available over the counter as a 1% lotion. For scabies mites, a stronger 5% cream is applied from the neck down, left on for 8 to 14 hours, then washed off. A single application is often enough for scabies, but a second treatment about a week later may be needed to catch any mites that survived as eggs.
Permethrin also treats pubic lice (crabs). The CDC recommends a 1% permethrin lotion applied to all infested areas, left on for the recommended time, then rinsed. A repeat treatment 9 to 10 days later is needed if live lice are still present.
The catch with permethrin is growing resistance. A large meta-analysis found that roughly 65% of head lice populations worldwide now carry genetic resistance to permethrin. In the United States specifically, one study found resistance genes in over 98% of lice sampled. Before 2004, resistance rates sat around 33%. After 2015, they climbed to 82%. So if permethrin doesn’t seem to be working on head lice, resistance is the likely reason, and switching to a different agent makes sense.
Pyrethrins With Piperonyl Butoxide
The other over-the-counter option for lice is a combination of pyrethrins (natural insecticides from chrysanthemum flowers) and piperonyl butoxide, which boosts their effectiveness. This is available as a mousse or shampoo and works against head lice and pubic lice. However, pyrethrins share a similar mechanism to permethrin, so lice that resist one tend to resist the other. The same resistance trends apply here.
Prescription Agents for Lice
When over-the-counter products fail, several prescription options offer different mechanisms of action that bypass resistance.
Spinosad 0.9% suspension is one of the strongest prescription choices. It kills both adult lice and their eggs, which means most people don’t need to comb out nits after treatment. In clinical trials, 85% of patients treated with spinosad were lice-free after 14 days, compared to just 44% of those treated with permethrin. Three out of four people needed only a single application. It’s approved for anyone aged 4 and older.
Ivermectin lotion 0.5% is applied to dry hair, left on for 10 minutes, then rinsed. It works through a different mechanism than pyrethroids, making it effective against resistant lice.
Malathion lotion 0.5% is effective but comes with a notable safety concern: it’s flammable. You cannot use hair dryers, curling irons, or any open flame while the lotion is on your hair or while your hair is still wet with it. No smoking either. It’s not recommended for infants under 1 year old, and use in children under 6 requires a doctor’s guidance.
Benzyl alcohol lotion 5% suffocates lice rather than poisoning them, which means resistance isn’t a concern. It does not kill eggs, so a second treatment is needed.
Oral Ivermectin for Stubborn Cases
Oral ivermectin is a systemic option, meaning it works from inside the body. It’s used for both scabies and lice when topical treatments aren’t practical or haven’t worked. For lice, it’s considered a second-line therapy. A single weight-based dose is given, with a second dose a week later if live lice persist.
For crusted scabies, a severe form where thousands of mites infest the skin, oral ivermectin is combined with topical permethrin because the thick crusts prevent cream from reaching all the mites. Oral ivermectin is not recommended for children weighing under 15 kilograms (about 33 pounds).
Dimethicone: A Physical, Non-Pesticide Approach
Dimethicone is a silicone-based lotion that kills lice by coating them and disrupting their ability to manage water, essentially suffocating them. Because it works physically rather than chemically, lice are unlikely to develop resistance to it. Clinical trials of 4% dimethicone lotion report cure rates between 69% and 92% after two applications a week apart. It’s a particularly good option when you want to avoid insecticides entirely, such as for young children or during pregnancy.
Tea Tree Oil for Demodex Mites
Demodex mites are microscopic parasites that live in hair follicles and oil glands, most commonly around the eyelids and face. They’re a different problem from scabies or lice, and they require different treatment. Tea tree oil is the most studied natural agent against Demodex. It’s typically applied as an eyelid scrub using pre-made wipes or foam.
The active compound responsible for killing Demodex is terpinen-4-ol, one specific molecule within tea tree oil. Research shows it’s the only component of tea tree oil that effectively kills Demodex at a 1% concentration. Treatment needs to continue for at least six weeks to cover two full life cycles of the mite. Tea tree oil should never be ingested, as it’s highly toxic if swallowed.
Essential Oils as Lice Treatments
Some essential oil blends have shown promising results against head lice. A randomized controlled trial tested an Australian essential oil solution containing eucalyptus oil and found it more than twice as effective as pyrethrins with piperonyl butoxide, with an 83% cure rate versus 36%. In laboratory testing, the solution achieved 100% kill rates on both lice and eggs after a single exposure. That said, essential oil products aren’t standardized the way pharmaceutical treatments are, so results can vary between brands and formulations.
Choosing the Right Agent
For head lice, starting with an over-the-counter permethrin or pyrethrin product is reasonable, but if it doesn’t work after proper use, resistance is likely and a prescription option like spinosad or ivermectin lotion will be more effective. For scabies, permethrin 5% cream remains the standard first treatment, with oral ivermectin reserved for severe or crusted cases. Pubic lice respond well to 1% permethrin or pyrethrins applied to the affected area, with a repeat treatment about 10 days later.
Regardless of which agent you use, treating the environment matters too. Wash clothing, bedding, and towels used in the days before treatment in hot water (at least 130°F) and dry on high heat. Items that can’t be washed can be sealed in a plastic bag for two weeks. For pubic lice, all sexual partners from the previous month need to be informed and treated simultaneously to prevent reinfestation.