Supplement for my Staffordshire Bull Terrier?

My Staffy has very itchy skin on her back and down her legs, she nibbles,scratches and licks.
I have been to the vets lots of times and I have Maleseb scrub to bath her with every 2 days,Stronghold drops and Viacutan pump to put on her food. The 1st vet I went to just said she had an allergy to something but was unsure and the 2nd vet said she had Sarcoptic Mange. She was treated with antibiotics as she had an infection from the scratching and she also gave me all of the above. This seemed to work and towards the end of last year she had most of her fur back and wasn’t itching. However, now we are in the summer months again, it has flared up. I have done some research on the internet as I have noticed that these flare ups only come in summer and having used all the potions the vet gave me and nothing has made a difference.
The thing that keeps cropping up is Hayfever and that dogs release histamines into their skin and that is what makes it itchy.
I have found a product from a company called Pooch and Mutt who claim to be able to alleviate the symptoms and allow the dog to be free from these symptoms and let the skin and coat recover.
Has anyone else got a dog with these problems or had and if so what are you/did you do for them?
Also can anyone vouch for Pooch and Mutt??
Any advice would be great and please don’t tell me to go to the vet as she is under her, Im just looking for anything extra for my dogs relief.
Thanks.

Didds; Dogs don’t just get born allergic to summer. Do ye feed the Dog raw? If not, I’d strongly suggest chucking the ” Complete Diet ” ye vet’s probably also selling ye and feed the animal raw flesh and bones.

Her system’s most likely reacting to a gross overload of the pure crap in her diet. Remove the source and she’ll be able to bring herself round, naturally.