[Ectoparasites. Part 1: lice and fleas].

Ectoparasites and epidermal parasitic skin diseases are a heterogeneous group of infections of the external layer of the skin. The most common forms world-wide are scabies, lice (Pediculosis capitis, corporis, vestimentorum and pubis), tungiasis and the hookworm-associated Larva migrans cutanea. The head louse is the most widespread parasite in children in Germany. The symptoms, apart from pruritus, eczematous skin eruptions and ictus reactions of the skin, are often unspecific and many differential diagnoses must be considered. Treatment of ectoparasites includes manual procedures, such as repeated cleansing and combing out of lice-infected hair and also local antiparasitic treatment with permethrin, pyrethrum extract, allethrin and dimeticon. Lindan which has been used for decades can no longer be used in medications after 2008 after a decision of the EU Commission. Failure of treatment of head lice can be a result of errors in the treatment which favor survival of the eggs, larvae or adults. This can be a result of too short reaction times and too economical use or unequal distribution of medications, excessive dilution due to wet hair or omitting repeated treatment stages. Additionally resistance of head lice to pyrethrum is a known phenomenon and has been reported in several countries.