sores on schnauzer

Question
I have a black and silver female schnauzer that is about one and a half years.  When she was about 8 months of age she got these sores on the tip of her hers that got infected and I had to take her to the vet.  They cleaned them out and gave me antibotic cream to put on them.  They cleared up in about a week.  Recently she is developing the sores again.  She has recently been to the groomers and when I got her back her I notice the next morning that her ears where covered with rwas spots that were scabby looking and hurt to touch.  I've been cleaning them and putting the antibotic cream on them but she now has a bump on her head that is scabby and big.  I've changed her food because the groomer which is a breeder of schnauzer told me it may be a food allergy.  So we are trying that. She does itch other parts of her body like her feet and tail.  Is there any auto immune diseases that start this way, with sores on there body? Should I go get her blood work done?  Please if anyone has had this problem before and know what to do please let me know!
Thank you,
Rachel

Answer
Hi,
There are many things that can cause the sorts of sores you are describing.  Food allergies is indeed one of them.  When changing food make sure to change to a holistic variety steer clear of canned food completely and dont feed anything with Corn as one of the ingrediants as most dogs are intolerant to corn to some degree.
Schnauzers do have skin problems quite commonly and allergic disorders to fleas, house dust, grass seeds etc are not uncommon.
Start by treating for parasites with a solution procured from the vet (the ones you can buy at pet stores are useless, the drugs that really work are prescription only and can only be supplied by a vet.)  This problem seems unlikely but is still a possibility.  
The next step is to treat for both bacterial and fungal infection since the sores could very easily be caused by either of these.  You vet will help you with prescriptions.
A vet check for demodectic mange may be a good idea.  These parasites can live on a dog undetected while the dog is healthy but may cause a problem if the dog is otherwise immunocompromised such as if they catch an infection or get pregnant.  These are notoriously difficult parasites to get rid of so the quicker they are attacked the better.
If none of these things are the problem then the next stop is allergies, you can have an allergy test done at the vets and in severe cases they can produce a vaccine for the dog against the allergen.  You vet will talk to you about whether or not this is appropriate.
Autoimmume disease is possible but this is at the bottom of the list of possibilties and your vet will explore this possibility with you when all others have been exhausted.
Hope this helps
Sarah