My cat had a severe reaction to it within 2 hours of putting it on
This was not a good use of money...I bought a pack of two collars and put them on my two cats. The boy had a reaction to his - he started running around very stressed, acting bizarre and out of character, he disappeared in the flat for an hour, then came running back out in a panic, his eyes were almost swollen shut, and he was in a panic to get the collar off. The collar cannot be removed once you put it on...you have to get scissors to cut it off.I cut it off immediately and he recovered.