I used the flea drops on my two babies a couple years ago and within a day my male started to lose hair where the drops go. Within a few days he had huge bald spot and chemically burnt skin. Fast forward to last year my partner had noticed a flea on one of the cats so rushed right out to get some shampoo…. Huge mistake he bought the harts brand and by the time I got home both of my kitties were in full blown seizures. Thankfully they both lived but not without issues my male is scared of his own shadow and never used to be and my female hides constantly and never used to.