Sudden Hair Loss On Legs

Dog with sudden hair loss… Can demodex develope at a old age?
I have a 6yr old boston terrier. She always had a shiney healthy coat. The last year or so we have been having a on going battle with her skin/coat. She gets her belly red and dry looking and she started loosing fur on her hind legs and butt area. I started giving her skin and coat tabs along with baths and using a sensitive skin moisterizer on her skin and her skin isnt red anymore but she continues to loose hair more and most and it has spread up to her shoulder area now.
The only thing i could think of is Demodex mange. She was put on antibiotics to treat any skin infections and bactirial (spelling?) issues. No improvement. I was going to order a gentle mange product and start using it. But would a healthy dog just suddenly after 6yrs get mange? Demodex is a immune disorder mange there born with. So im at a loss here
Well yes older dogs can get it also but if they have a low immune system it could cause the hair loss and just now start to show. I would take her to the vet. But my Papillon is doing the same thing and a friend of mine dog is doing it also so maybe its just the heat? not sure but she got some dog shampoo with oatmeal in it its suppose to help for dry skin.
Good luck
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