A quick read says rabies vac can indeed give reaction like this, and that small dogs in particular may be more likely to react. Also that combo shots are more dangerous for them.
If they don’t think it’s allergy why did they give you Benadryl? Just to be sure?
Check out the info. on vaccines from holistic vet Karen Becker on her site: www.healthypets.mercola.com
Here is a search link for some of her articles on vaccinosis:
Bottom line: the head immunologist, Dr. Ron Schultz, advises that vaccines should NOT be given yearly, but titering should be done at intervals reflecting the current protocols (3 years for Rabies and for Distemper/Parvo). As the dog gets older (over 10 years old), those titers can be repeated more often (yearly) as dogs tend to lose some of their immunity as they age, just as humans do.
If a dog has a reaction (and no, a week is not “too long” for a reaction — not at all!!), do not vaccinate again. Use titers and if you absolutely MUST vaccinate for something be sure it is a single vaccine and not a “mombo combo”. Bordetella is pretty useless and shouldn’t be administered unless you have to do so for boarding purposes. It will not prevent kennel cough, but supposedly makes the case milder if caught. The problem is it has a low lasting immunity and must be administered about every 6 months....which is a lot for a vaccine. The purpose of the bordatella shot is for liability purposes for businesses and has nothing to do with the health of the pet. Most dogs can throw off a case of kennel cough fairly easily if their immune system is not compromised. Hope this helps!