Effective Stress Reduction for Use Both at Home & On the Go! Vet Recommended. Sustained Release Pheromones Proven to Modify Behavior. Recommended for Problems Such as: Separation Anxiety, Destructive Behavior, Inappropriate Marking. Lasts Up to 30 Days. Effective at Home & On the Go. For Kittens & Cats up to 15 Neck Ask a vet: How quickly will the cat respond once the SETTLEdown ™ Pheromone Collar is placed on the cat s neck? When the collar is placed, the perception of the pheromones by the cat is immediate. However, as in every behavior program,.