Histiocytosis is a medical condition where certain cells in the body, called histiocytes, multiply abnormally and cause inflammation and damage. It can affect different parts of the body, leading to various symptoms and complications.
In temperate regions of the world, cutaneous reactive histiocytosis affects mainly young dogs, often Collies, Springer Spaniels, and Golden Retrievers. (cedarbayouanimalclinic.com)
Infants with widespread seborrheic dermatitis and other symptoms, such as failure to thrive or chronic diarrhea, may have other conditions, such as Leiner's disease or Langerhans cell histiocytosis X. (verywell.com)