Have their been any food changes? How about changes in the home that could cause allergies...did you recently wash his bedding in a new detergent, get him a new shampoo, etc.? When it has happened in the past has it always been fall?
There is also the possibility of something like mange. Has he been to a pet store, vet office, or dog park recently? Has he had (diagnosed) mange before? Has he been under any stress lately? If it were something like demodectic mange it could crop up every once in a while when the dog is stressed or his immune system is down.
For some reason the appearance around the eyes reminds me of demodectic mange more than allergies, but know way to know without a skin scraping.