These gels have active ingredients of peppermint oil, clove and lemon grass oil and can kill your pet. I used the Sergeant’s version but I see that Sentry also uses this formula. I tried this on Smokey the cat and she started terrible drooling and almost running into walls with in a minute of two. I covered the oil with dawn dish soap and rinse her for quite awhile in the tub. She seems to have recovered completely and has even forgiven me about the bath, but I tell you it gave me quite a scare.
I had no idea that anything like this could happen and we were lucky I got that crap off her so quickly because many people are losing both dogs and cats to these flea gels. I will use DE and get rid of these gels, and let every store know this stuff is dangerous to pets.