Stat Consult ——eggs initially translucent, attached to base of hair shaft by glue-like substance from louse ——empty egg casings are white, viable nits pigmented ——eggs incubate (need heat of scalp) and hatch in 7-12 days ——female nymphs grow for about 9-12 days, then mate and lay eggs • no transmission of other disease agents to humans History
• Chief concern (CC) ——scalp pruritus (due to injected louse saliva) ——“something crawling on my head” ——often asymptomatic • Social history (SH) ——ask if any cases of head lice at child’s school or day care • Physical ——HEENT ■■ primary findings are nits or adult lice (may require magnifying lens) »»nits at proximal ends of hair shafts »»viable nits most easily seen at nape of neck or behind ears at hairline »»height of nits above scalp due to hair growth indicates duration of infestation (1 cm/month) »»number of lice found may vary by cultural hair grooming practices ■■ secondary skin reactions to lice or scratching »»excoriation »»secondary bacterial infections ——Neck ■■ posterior cervical local adenopathy if secondary skin infection Making the diagnosis
• presence of live adult louse, nymphs, or viable-appearing eggs (nits) on head • nits appear viable if found <1 cm of scalp, firmly attached to hair, and have microscopic “eye spot” Differential diagnosis
• other causes of scalp pruritus ——irritation from hairstyling products ——allergic contact dermatitis ——seborrheic dermatitis • dead eggs or empty egg cases • “pseudo-nits”—nodules resembling nits (can be easily separated from hair) ——dandruff
——dried hairspray ——dirt, lint, sand ——white piedra—fungi (Trichosporon beigelii) ——hair casts—desquamated cylindrical epithelial cell plug that encircles hair, easily movable Testing overview
• inspection ——wet and comb hair, remove tangles ——examine under strong light and with magnifying glass ——use fine-toothed comb (teeth 0.2-0.3 mm apart) ——insert comb near crown at scalp ——comb entire head systematically at least twice ——examine comb after each stroke Treatment overview
• topical pediculicides ——optimal pediculicide dependent on local resistance patterns ——universal retreatment recommended in 7-10 days if live lice seen ——permethrin 1% applied to towel-dried hair, leave for 10 minutes then rinse ■■ F DA approved in adults and children ≥2 months old ■■ recommended by AAP as treatment of choice for head lice ——malathion 0.5% lotion applied to dry hair, then after 8-12 hours washed off with shampoo ■■ FDA approved in adults and children ≥6 years old ■■ recommended when permethrin resistance suspected ——benzyl alcohol lotion 5% lotion applied for 10 minutes ■■ FDA approved in patients ≥6 months old ——ivermectin 0.5% lotion applied to dry hair for 10 minutes ■■ FDA approved in patients >6 months old ——other topical treatments ■■ dimethicone 4% lotion ■■ spinosad 0.9% topical suspension (FDA approved in patients ≥4 years old) ■■ pyrethrins with piperonyl butoxide applied to dry hair for 10 minutes ■■ lindane no longer recommended for use as pediculicide • occlusive agents may be effective including ——melaleuca plus lavender oil ——coconut plus anise oil ——petroleum jelly • nit removal ——evidence limited and inconsistent
50 THE CLINICAL ADVISOR • FEBRUARY 2018 • www.ClinicalAdvisor.com