Hair loss

Hi. My 4 yr old long haired cat started losing hair on his tail, starting from the tip, about 2 weeks ago. Still has hair although it's thinned out quite a bit. Haven't noticed abnormal amount of grooming or any behavior changes. I'm concerned for him of course but also hope it's not contagious since we have a second cat. They are both strictly inside cats. I don't have money to have a vet run tests so I'm trying to do what I can here. Anyone seen this before? Thanks so much

Have you checked for Fleas?

Yes I've checked. Can't see any. I've been watching him a lot this morning and he is grooming more than normal. I tried to get a hold of him to really look at his tail but he isn't letting me.

he could be allergic to something  either his flea medication

or something he came into contact in your house,

might also be stress related my sister had a cat wo lost his fur 

after he was given flea meds i think it was drops from the vet

How old is he? My last cat started getting bald spots and I could not figure it out. Finally I put him on a supplement for joint pain and the hair grew back in almost immediately. Turns out he was licking his sore joints poor baby. I hope you can figure it out!