Allergies (effecting skin) in an older Dalmation?

My boyfriend occasionally dogsits an older dalmation, the owners say he has allergies to tons of things and is on pills (every morning) and occasionally, I'm assuming when things get worse, a shot they have.
The dog has sores on his body that he constantly licks, nibbles, scratches. I'm assuming the sores come from his licking as they will appear suddenly, etc... I thought I remembered reading that dogs will lick constantly from boredom. (I'm in no way ruling out allergies as the dog is not mine and the owners have no reason to lie.)
It simply seems to me that there could be something they could do for the sores aside from a pill every morning!! Is there an ointment? Is the dog still allergic to something not being treated? Could the sores be from the medication? They look raw and painful!!
Also, this could be a very sensitive question, the dog IS quite old however still acting somewhat young, when is the right time to send your pet to the rainbow bridge?
Answers:
The sores are most likely from him scratching and licking. Licking can become a habit, too. The best way to treat allergies is having an allergy panel run by the vet. When the results come back, reduce/eliminate whatever allergens you can from his diet and environment. The results will tell you exactly what bothers him, no more guessing. If they've tried everything (truly everything) and the dog's suffering, then it might be time. The vet should help determine that, however.
Test Info: http://www.vetallergy.com/petowners.php...
ETA: I don't know if it's true or not, but from what I've read and heard...food allergies only account for ten percent of the allergies. I tend to believe it though, because most of the people who say their dog(s) have food allergies have never had them tested. I know my dog has a few diet related, but the environmental ones win by a landslide...house dust/mites, cotton, many types of trees, many types of grasses, many types of weeds, many types of fungi, etc.

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Dalmatians are know to have separation anxiety. Also can be a nasty habit too. If the owner are alreay giving the dog meds than their is reallly nothing more to be done. Food allergies are the number 1 cause of allergies in dogs. It's walking on thin water with a dog that is not yours and to suggest to some owner to have the dogs allergy tested may not be looked on to well by them. If your very good friends with them than a suggestion to have the dog tested would be a good one.