Ketoconazole shampoo primarily treats dandruff, a condition that causes itching and flaking of the scalp, says WebM. Ketoconazole shampoo also controls pityriasis, an affliction affecting skin coloration on the upper torso, arms and legs.
Both dandruff and pityriasis are fungal infections of the skin, according to WebMD. The anti-fungal ketoconazole effectively prevents the growth of fungus, but fungus often returns when the treatment stops. Ketoconazole shampoo comes in two different strengths, over-the-counter at 1 percent ketoconazole and prescription strength at 2 percent.
Common side effects include irritation of the scalp, tenderness or changing hair texture, notes WebMD. Serious allergic reactions occur in rare incidences.