The FEI has issued a warning to the equestrian community about synephrine, a banned substance listed on the Equine Prohibited Substances List. A high number of samples taken from horses in the UK recently have tested positive for the substance. Investigations as to the specific source responsible in this case are continuing but the FEI is warning that in fact synephrine is something that is commonly found in all horse’s environments.

Synephrine is a stimulant that can cause blood vessels to constrict, cause an increase in heart rate and is often used as a weight loss agent. In certain areas it can be found in plants such as the common rush and the leaves of citrus trees. Synephrine has also been found in Teff grass hay. It is an ingredient in some herbal and nutritional supplements, and is commonly found in the peel of oranges which is often used as a flavouring agent.