According to my vet - thought I had posted it on here? I was told in Dec when I asked with Shadow (I didn't know when kitts went from monthly to 3 monthly cos I dont deal with them normally!!), and when I got the girl's Milbemax last month, it is on the printed label from teh vets - it is for human and animal safety - vets say it is only really necessary if you have young kids though, they still do 3 monthly for their own pets, so I shall, I dont have any young kids, and the girls idea of birds are those things they sit and chatter to from the inside!!