We suggest that demodicosis be divided into both primary and secondary types. The usual etiological agent of primary demodicosis is D. folliculorum, which causes an erythemato-squamous eruption in the facial T-zone. The rash starts on unaltered skin and covers 8 - 15 % of the face. Pruritus accompanies the onset of the rash, while erythema is first apparent after papulo-pustules are seen and disappears after treatment. Half the patients show seasonal exacerbations. Secondary demodicosis is usually caused by D. brevis and characterized by a symmetrical malar papulo-pustular eruption. It develops on diseased skin and covers 30 - 40 % of the face. Pruritus starts after the lesion exacerbation, but erythema precedes the papulo-pustular phase and persists after treatment. Most patients flare during the summer. The facial distribution, seasonality and pathogenesis, as well as the species of mite involved, must be taken into consideration in separating the various forms of demodicosis.