puppy allergies

Question
Hi I have a question about my 8 month old Westie. He has had a skin problem for a few months ago that my vet said was most likely allergies. And that I needed to switch him to a Lamb & Rice dog food I have done so and his red and itchy skin has gotten better. Not completely but it has improved. But today we went to a friends house & he ate another dogs regular food. A few hours later his ear was bleeding from him scratching so bad and his paws are very red. Is there anything I can do to help him? And how long will it last? Also about what age should a dog be completely potty trained? He doesn't ever go in my house. But when we visit others he always does.

Answer
My boston terrier female is 7 months old and Fully potty trained. Give him Benadryl allergy pills for people, they are in a pink and whtie box, be sure to get the 25 ML ones nothing higher...I give these to my jack russell terrier all spring summer and fall as he has seasonal allergys and gets just like your dog has broke out with, one or two of the 25 ml pills daily will calm the itchiness and scrtaching and allow the skin to heal.