Supplements Definitive Management of Head Lice in the Era of Pediculicide Resistance
Clinical Update on Resistance and Treatment of Pediculosis capitis
Head lice are extremely host-specific,
feeding only on humans, and have demonstrated
increased resistance to pediculicides.
Current clinical data demonstrate
that most pediculicides do not meet advertising
claims of "killing lice on contact."
Slow pediculicidal action, ineffective formulations,
and sublethal residue on the hair
and scalp have contributed to resistance
over time. Malathion 0.5% is the only pediculicide
that has retained its efficacy, killing
both lice and nits.2,3 Other commonly used
products have demonstrated resistance in
the United States. Although malathion
resistance has been documented in the
United Kingdom, the formulations there
are very different from OVIDE that is sold
in the United States. The US formulation
includes synergistic components to deter
the development of resistance. When US-manufactured
OVIDE was tested on
malathion-resistant lice from the United
Kingdom, it maintained its efficacy.7 Recent
data suggest that a decreased application
time for OVIDE is effective without producing
residual effects.5 The reduced application
time is beneficial for the pediatric
population, particularly in terms of limiting
the risk for potential adverse events, such as
itching or burning of the scalp.
Of particular interest is the failure of nit
combing to produce better outcomes, even
when used as an adjunct to pediculicide
therapy.4 Schools and organizations often
advocate nit combing as a safe and effective
way to eradicate lice and nits. Study results
suggest that nit combing is not effective.
The clinical history of pediculicides and
the increase in resistance over time strongly
suggest the need for better management of
therapies that remain efficacious, such as
malathion 0.5%. Currently, it is the only
pediculicide to demonstrate no resistance
and no change in efficacy; however, overuse
of malathion 0.5% may lead to resistance in
the United States as it has in other countries.
Since malathion 0.5% is a prescription
product, physicians are urged to regulate its
use and to educate patients and others, such
as school administrators and public health
policy developers, about the proper use of
1. Meinking T, Taplin D. Infestations. In: Pediatric Dermatology. 3rd ed. Schachner LA, Hansen RC, eds. Edinburgh: Mosby; 2003:1141-1180.
2. Meinking TL, Entzel P, Villar ME, Vicaria M, Lemard GA, Porcelain SL. Comparative efficacy of treatments for pediculosis capitis infestations: update 2000. Arch Dermatol. 2001;137:287-292.
3. Meinking TL, Serrano L, Hard B, et al. Comparative in vitro pediculicidal efficacy of treatments in a resistant head lice population in the United States. Arch Dermatol. 2002;138:220-224.
4. Meinking TL, Clineschmidt CM, Chen C, et al. An observer-blinded study of 1% permethrin creme rinse with and without adjunctive combing in patients with head lice. J Pediatr. 2002;141:665-670.
5. Meinking TL, Vicaria M, Eyerdam DH, et al. Efficacy of a reduced application time of OVIDE® Lotion (0.5% malathion) compared to Nix® Crème Rinse (1% permethrin) for the treatment of head lice. In press: Ped. Dermatol.
6. Taplin D, Meinking TL, Castillero PM, Sanchez R. Permethrin 1% Crème Rinse for the treatment of Pediculus humanus var caputis infestation. Pediatr Dermatol. 1986;3:344-348.
7. Downs AM, Stafford KA, Harvey II, Coles GC. Evidence for double resistance to permethrin and malathion in head lice: reply from authors. Br J Dermatol. 2000;142:1067.