The disease is characterized by the proliferation of mast cells (cells containing histamine and other enzymes) in the skin or internal organs, which are involved in the allergic reaction. It can appear anywhere on the skin as a brown, smooth spot on the surface. After mechanical irritation (Darier's sign), redness up to a pimple forms on the affected area. When internal organs are also affected, a general allergic reaction of the anaphylactic shock type may occur due to significant release of histamine. Treatment is symptomatic. It is important to avoid certain medications, foods with a high histamine content (sausages, canned foods, sea fish, poppy seeds, honey, citrus, cocoa, spicy foods, nuts, tomatoes, strawberries), physical influences (mechanical irritation, hot baths, hot foods and drinks, sunbathing), which can irritate the mastocytoma and cause the release of histamine with a subsequent reaction. Symptoms may disappear spontaneously after several months or years.