Occasionally horses can get stung by honeybees. Bee venom is made up of large-molecular-weight proteins, peptides, various amines, simple organic molecules and other bioactive elements. Most of the time, if it is a single sting, the horse might experience a mild local reaction in the form of pain, swelling, redness, itching, and a wheal surrounding the wound made by the stinging apparatus. However, sometimes a horse may have an allergic reaction to the venom, which can be life threatening to the animal without early recognition of clinical signs and prompt treatment.
The severity of the reaction is directly related to the dose of venom and associated clinical signs. The lethal dose of honeybee venom is estimated to be 20 stings per kilogram of body weight.
Two types of reactions are typically associated with bee stings---local reactions or serious systemic illness, usually caused by IgE-mediated anaphylaxis rather than by toxic envenomation. Possible systemic illness effects include intravascular haemolysis, rhabdomyolysis, acute renal failure, myocardial damage, hepatic injury, acute respiratory distress syndrome and disseminated intravascular coagulation.