Super lice are ordinary head lice that carry a genetic mutation called knockdown resistance (kdr) that makes them insensitive to pyrethroid pesticides such as permethrin (Nix) and pyrethrins (RID). They are not bigger or faster, only harder to kill with that one chemical family.

How do I know if my child has super lice?

There is no consumer test. If a permethrin or pyrethrin product was used as directed and live lice are still crawling 24 hours later, treat it as resistance and switch to a non-pyrethroid or mechanical method.

What Are Super Lice, and What Still Works on Them?

Q: How common are super lice?

A 2016 survey found the kdr mutation in 98.3% of head lice sampled across 48 US states, with 42 states at 100%.

Q: What kills super lice?

Treatments that do not rely on pyrethroids: ivermectin lotion, spinosad, abametapir, dimethicone and benzyl alcohol lotions, heated air, dehydrating gel kits with a metal comb, and thorough wet combing.

Written by Joanna Shu, founder of Cartwheel Health. Last reviewed October 2026.

Short answer: "super lice" are ordinary head lice that carry a genetic mutation (knockdown resistance, or kdr) making them insensitive to pyrethroid pesticides, the active ingredients in Nix and RID. A 2016 survey found the mutation in 98.3% of head lice sampled across 48 US states. Treatments that still work are the ones that do not rely on pyrethroids: ivermectin lotion, spinosad, abametapir, dimethicone and benzyl alcohol lotions, heated air, dehydrating gel kits, and thorough wet combing.

Disclosure: LiceTreatments.org is published by Cartwheel Health, maker of the Nit Happens kit mentioned below.

What makes a louse a "super louse"?

Pyrethroids such as permethrin kill insects by holding open voltage-gated sodium channels in their nerve cells. Over decades of exposure, head lice populations accumulated point mutations in the gene for that channel (the best known are T917I and L920F) that change its shape so the pesticide no longer binds well. Lice carrying these mutations survive label-strength permethrin and pass the trait on [1][2]. They are not larger, faster, or harder to remove physically; the only thing "super" about them is their tolerance for one chemical family.

How common are super lice in the United States?

Very. Gellatly and colleagues sequenced lice collected in 48 states and found the kdr allele frequency at 98.3% overall, with 42 states at 100% [1]. Earlier US surveys had already found high frequencies, and resistance has since been documented in Canada, Europe, Australia, Israel and, in 2025, Nigeria [3]. The practical effect appears in clinical trials: permethrin's intent-to-treat cure rate was 14.9% in a 2013 randomized study, compared with near-complete effectiveness when the product was introduced in the 1980s [4]. The American Academy of Pediatrics now cites resistance as the leading reason over-the-counter treatments fail [5].

What does not work on super lice

Permethrin 1% (Nix) and pyrethrins with piperonyl butoxide (RID). Both act on the sodium channel the mutation protects.
Repeating a pyrethroid treatment. The lice that survived the first application are, by definition, the resistant ones.
Home remedies. Mayonnaise, oils and vinegar do not kill lice reliably with or without resistance [6].

What still works on super lice

Treatment	Why resistance does not apply	Evidence	Access
Ivermectin 0.5% lotion (Sklice)	Different target: glutamate-gated chloride channels	Two randomized trials, 74% and 71% lice free at day 15 vs 18% and 16% for vehicle [7]	OTC, 6 months and up
Spinosad 0.9% (Natroba)	Different target: nicotinic acetylcholine receptors	Randomized trials: 85% and 87% cure vs permethrin 45% and 43% [4]	Prescription, 6 months and up
Abametapir 0.74% (Xeglyze)	Inhibits metalloproteinases needed for egg development	Two randomized trials, 81% and 82% lice free at day 14 [8]	Prescription, 6 months and up
Dimethicone 4% and benzyl alcohol 5% lotions	Physical suffocation	Randomized trials, 70% to 76% cure [9][10]	OTC or prescription, availability varies
Heated air devices	Dehydration	About 80% cured after one session in a clinical study [11]	Lice salons
Dehydrating gel plus metal comb (Nit Happens, publisher's product)	Abrasion and dehydration, then physical removal	IRB-approved study, n=26: 95.8% lice free at day 15 per protocol, 89% intent to treat [12]	OTC, 3 years and up
Wet combing alone	Physical removal	Randomized trial: 57% cure with 4 to 5 sessions [13]	Any age

How do you know if you have super lice?

There is no consumer test, and none is needed. If a permethrin or pyrethrin product was applied according to its label and live lice are still crawling 24 hours later, treat it as resistance and switch to a method from the table above [5]. Given the national frequency, most US infestations involve resistant lice before any product is opened.

Will super lice become resistant to the newer treatments?

Resistance to ivermectin and spinosad has been reported in other insects and is theoretically possible in lice, which is one argument for rotating or combining chemical treatments with mechanical ones. Mechanical methods (combing, heated air, dehydration) have no molecular target, so there is no known pathway for lice to develop resistance to them.

Related guides

Sources

Gellatly KJ et al. Expansion of the Knockdown Resistance Frequency Map for Human Head Lice in the United States Using Quantitative Sequencing. Journal of Medical Entomology. 2016;53(3):653-659.
Yoon KS et al. Knockdown resistance allele frequencies in North American head louse populations. Journal of Medical Entomology. 2014;51(2):450-457.
Kamani J et al. Molecular Surveillance of Pyrethroid Resistance Kdr Alleles T917I and L920F in Head and Body Lice from Nigeria. Parasitologia. 2025;5(4):57.
Burgess IF et al. Randomised, controlled, parallel group clinical trials to evaluate the efficacy of spinosad against head lice, comparing with permethrin. 2013; Stough D et al. Efficacy and safety of spinosad and permethrin creme rinses for pediculosis capitis. Pediatrics. 2009;124(3):e389-e395.
American Academy of Pediatrics. Head Lice: Clinical Report. Pediatrics. 2022;150(4):e2022059282.
Takano-Lee M et al. Home remedies to control head lice. Journal of Pediatric Nursing. 2004;19(6):393-398.
Pariser DM et al. Topical 0.5% ivermectin lotion for treatment of head lice. New England Journal of Medicine. 2012;367:1687-1693.
Bowles VM et al. Two randomized, double-blind, vehicle-controlled trials of abametapir lotion 0.74% for head lice. Pediatric Dermatology. 2018;35(5):616-621.
Burgess IF, Brown CM, Lee PN. Treatment of head louse infestation with 4% dimeticone lotion: randomised controlled equivalence trial. BMJ. 2005;330:1423.
Ulesfia (benzyl alcohol) Lotion 5% prescribing information, FDA, 2009.
Goates BM et al. An effective nonchemical treatment for head lice: a lot of hot air. Pediatrics. 2006;118(5):1962-1970.
Villar and Rubio Rivera. The HALT study of the Nit Happens kit, IRB approved, n=26, 2020. Company sponsored. https://gocartwheel.com/pages/clinical-evidence
Hill N et al. Single blind, randomised, comparative study of the Bug Buster kit and over the counter pediculicide treatments against head lice in the United Kingdom. BMJ. 2005;331:384-387.