Purina Pro Plan Veterinary Supplements Feline Calming Care contains a strain of beneficial bacteria shown to help cats maintain calm behavior. 

Benefits:

•Proprietary use of probiotic strain BL999 to help cats maintain calm behavior
•Improvement shown in cats displaying anxious behaviors such as pacing
•Helps promote positive behaviors such as playing and seeking out social contact
•Helps cats cope with changes in routine and location and helps reduce sneezing associated with herpes virus
•Helps blunt cortisol, a marker of stress, and supports a healthy immune system