I have a dog with itching problem. I use canine advanitx on her and have also been giving her supplements for skin and coat.
I understand that benadryl(diphenhydramine) helps provide relief. Drs Foster/Smith sells benadryl in 50 mg caps. that is plenty for a person, it seems like a lot for an animal.
I am interested in hearing what other dog owners have had success with, in terms of treating canine skin allergy symptoms?
Change her food to Nutra Max Natural Choice. My dog itched, lost his hair, had hot spots, etc., until I changed his food. This food worked wonders for years!!
I'd suggest getting a consultation with your vet along with an exam. Some dogs are food allergic, in which keeping them on a specific food can cure the problem. Some have environmental allergies – species of grasses, trees, pollens…we had a poor cocker who came in once that was found to be highly sensitive to Bahaya grass, oak pollen and HUMAN DANDER 
He obviously started allergy vaccine! LOL
The Benedryl would be an option for sporadic relief, as well as PERHAPS steroids (which most vets don't like giving, they can mess up the systems in dogs and especially cats), but I would definitely call the vet before giving anything, as your vet knows the history, age, weight, any other medical problems the pooch may have that may conflict with anything you may goodheartedly want to give him.
Good Luck!
My dog had this when he was a puppy. we took him into the vet and the vet gave us some pills to give him. It worked!
Benedryl is very safe for your pet, only side affect would be possible drowsiness. the dosage is 1 MG per pound of pet so 25 pound dog would get 25 MG of benedryl. Get dog on a GOOD dog food and may need a vitamin supplement also.
Both of my dogs have allergies and to different things. My Pit has food allergies as well as allergies to flea control. My Lab as envirnomental and has had a hard time. the Pit was easy to fix he is on an excellent diet ( Royal Canin we tried everything including Holistic foods and Royal Canin is the only one that worked). we also only use all natural flea control ( no chemicals) anything else cause him to have an allergic reaction. he is fine that way and no drugs. My Lab was having extreme allergy problems and was on Benedryl and steriods. I hated the side effects of both and could not stand how awful he felt. he is on Royal Canin and a Holistic blend- Raw Intstinct. I really like the Holistic foods so i tried Holistic treatment and it is the first Meds and treatment that works. I thought nothing would work but this does and it is all natural and NO SIDE EFFECTS. FInd and an all natural pet store or go to azmira.com. Azmira is the manufacturer of the products. My dog get Yucca Intensive drops ( all natural steriod but no side effects) and he gets Allerg' Free (which replaces the Benedryl and is all natural) This combination is absolutely amazing and my dog is doing EXCELLENT and no longer scratching himself to death. Nothing prior to this worked and I spent hundreds at the vet. I also use Richard's Organic Incredible Skin Spray, I tried everything known to man and this stuff is absolutely amazing/ It is also all natural and has all natural antibiotics in it to stop and aviod infection. your dog will instantly stop itching. You can only find it at an all natural pet store but it is well worth it. Trust me I tried everything prior to this regime and nothing helped my Lab until now. Nothing the vets did worked it only caused health problems but now my dogs are itch free and happy. good Luck.
Go to earthclinic.com/pets for great info and home remedies that really work for many skin conditions!!!