Shetland ponies may offer clues to help allergy sufferers, Edinburgh University researchers have found.
The experts said the horse immune system could respond to midge bites in a way that prevented, rather than triggered, allergic reactions.
The study of Shetland ponies found horses responded to the irritants in midge bites but their immune systems acted in two different ways.
Some had itching while others were able to prevent an allergic reaction.
Those that did not react were somehow able to block different immune cells that would otherwise trigger symptoms.
Edinburgh University scientists hope this knowledge can be applied to humans, so that the immune system could be primed to respond in a way that does not set off a reaction, possibly preventing people developing allergies.
Dr Dietmar Zaiss, of Edinburgh University's school of biological sciences, said: "To our knowledge, this is the very first study of a natural allergic disease in which we can show that immune responses to allergens can take two directions, either leading to allergy or to tolerance.
"We believe this finding could have direct practical implications, for example by helping immune responses to choose the 'right' direction in individuals who we would like to protect from developing occupation-associated allergies."