University of Massachusetts Amherst researchers have made a promising discovery that could lead to the development of a natural and effective tick repellent. They have shown that a naturally occurring compound secreted by the skin of donkeys effectively repels adult Ixodes scapularis ticks—the most frequent human-biting tick in the U.S. Commonly known as the deer tick, this species of arthropods is responsible for spreading Lyme disease, anaplasmosis and babesiosis—bacterial infections that can sometimes cause serious and long-lasting illness.

Currently, the most effective tick repellents contain ingredients like DEET and permethrin, which are safe when used as directed but are not benign or ideal, and some people simply don’t like to use them.

The sebaceous glands of horses and donkeys create secretions that keep their skin moist and include allomones, or chemical substances that affect the behavior of other plant and animal species. Previous research has shown that ticks that feed off horses but not donkeys will be repelled from horses when the horses’ smell is masked using one of the compounds, known as (E)-2-octenal, secreted by donkey skin.