Skin Ailments—Ectoparasites
Pediculosis (lice)
General—arthropod and obligate parasite which infests humans
Clinical—an allergic reaction to louse saliva produces pruritus; takes ≥2 weeks to develop
Etiology—lice species affecting humans include
Pediculus humanus capitis—head louse
Phthirus pubis—pubic louse (crab)
Pediculus humanus corpus—body louse
Transmission—person-to-person contact
Life cycle—egg firmly on hair shaft → nymph after approximately 7 days → mature after approximately 10 days
Risk factors—bedding/clothing changed infrequently, homeless
Diagnosis—lice or nits (viable eggs) seen on examination; excoriation may also exist
Treatment
Pediculus humanus capitis—head louse
Pyrethrum Insecticides (pyrethroids)
Permethrin topical (Nix) 1% cream q10d × two applications
Use after shampooing, leave in place for 10 minutes, rinse.
Pyrethrin topical (Rid) 0.33% foam q10d × two applications
Apply to dry hair, leave in place for 10 minutes, rinse.
Second-line agents for treatment-resistant head lice
Malathion topical (Ovide) 0.5% q10d × two applications
Apply to dry hair, leave in place for approximately 10 hours, rinse.
Lindane topical 1% shampoo × one application
Used infrequently because of neurotoxicity.
Oral agents
