But he has had infections before?....you said they were chronic.
Ear infections and feet licking are classic signs of allergy, which is sounds like you are aware of. Allergies are something we aim to manage because there is no cure. There is also no perfect way to manage them.
First, we need to get any secondary infections under control. Ideally you would take your boy to the vet and have his ears examined to make sure his ear drum is normal and a sample from the ear checked with a microscope to see if there are bacteria or yeast in them. Then ear drops with antimicrobals and cortisones would be prescribed. The otomax works great so you can start that twice a day. Since his ear drum has not be evaluated you need to monitor him for any hearing loss. Otomax is toxic
if there is a ruptured ear drum.
Regular ear cleaning is also critical. The medications do not work well if the ear is full of debris. You can get an ear clean from the vet or feed store, or you can mix 1/3 vinegar, 1/3 water, 1/3 rubbing alcohol. Fill the ear with the mixture, massage, and then wipe any debris out that you can see. Clean the ears at least once a week, more if there is a lot of debris.
If he has sores on his feet they are likely infected too and could use some oral antibiotics.
The second part is controling the allergies which can be very hard. A hypoallergenic diet
is important. It sounds like you are on one. I understand why you are using the activia as a probiotic, but I would stop it.....some dogs have dairy allergies. Get a probiotic that is not based in any beef flavor or yogurt. And make sure you are not giving your dog anything else....treats
or even your monthly heartworm preventative could be contributing to his allergies.
Also, he shoudl be on regular flea control (Advantage or Frontline) even if you do not see fleas. Even one flea bite can make his allergies flare up.
After fleas and food are taken care of we are left to deal with environmental allergies.....house dust mites, grass, pollen, etc. You can't keep your dog away from these so the itching has to be managed. Regular bathing, fish oil capsules, and antihistamines can help. If this doesn't help then Prednisone is great, but can not be used long term because of the side effects. Atopic works great, but is very expensive....$200/month or so. Allergy shots help, but you have to give him shots on a regular basis.
You should have a vet that you talk with and work with to develop a strategy for dealing with this. It is like to be a life long struggle.
I hope that helps.