'Heat' diarrhea in foals is an onerous but not life-threatening ailment, which indicates that it may be of osmotic origin. This was confirmed by a successful attempt, presented in this paper, to alleviate the severity and duration of foal heat diarrhea with the use of a typical absorbent, kaolin clay, as a feed additive, usually applied in feed production as an anticaking agent. Based on the present results, it can be concluded that treatment of foals maintained on different stud farms with a kaolin paste reduced the duration of heat diarrhea and alleviated its severity (P < 0.05 and P = 0.001). The observed action of kaolin clay, an excellent absorbent, suggests that the so-called heat diarrhea can be caused by disturbances in the intestinal osmotic balance at this specific age of foals. The use of this preparation can reduce the risk of secondary pathological viral or bacterial diarrhea and the requirement for veterinary intervention in foal management. It can also shorten the care period and increase foal well-being, essential for the normal development of a young horse. In addition, prophylactic application of an antidiarrheal preparation based on an industrial by-product, i.e. A cheap component, will reduce the costs of foal care.