Parasites are specialized creatures that live totally or in part at the expense of other species. Relevant to the skin are ectoparasites, especially arthropods and worms, which live permanently (scabies mites, head lice) or temporarily (bugs, fleas, ticks, harvest mites, cercaria) on or in the skin. During childhood pediculosis capitis, scabies, reactions to insect bites, trombidioses, and cercarial dermatitis play the most important role and are described below.