There are no known side effects to date. However, if a pet is susceptible to homeopathy, an improvement may be seen in as little as one dose, and if the medicine is continued at full dosing schedule, an aggravation of symptoms may occur. Ceasing to use medicine will alleviate symptoms. Some pets, especially cats, may salivate excessively, or in very rare cases, throw up. Putting drops on food/treat and letting sit for 20 minutes will prevent such a reaction.