Shi Tzu allergies

Question
I have a 10 ish year old shi Tzu (Teddy) he has had bad allergies his entire life since I have had him I got him when he was 3) but recently he has had rapid weightloss and his back legs have swollen and become scaly I have been washing him every other day with a mild oatmeal shampoo however last night when I bathed him I gently washed his back legs and there was a bloody pus type fluid coming from his feet where they were swollen. Help Teddy is a beloved pet and I am so worried about him !!!!

Answer
Has he been on medications like steroids for his allergies for a long time?  That may cvause it.  Also, many dogs with allergies also develop skin infections.  That can affect the feet.  Have your vet check for these things and also to check for demodex mange.  That can happen in the feet to swell (pododermatitis).