Itchy Golden Retriever. Although less common food allergies not only cause itching but as well diarrhoea. Your vet will prescribe antibiotics for this.

But even with the best traits of a Golden Retriever there are bad things to take note of. If after a monthly bath your golden retriever is still itchy talk with your vet. Yes you can give Benadryl to your golden retriever according to the American kennel club Benadryl is commonly used to treat itchiness that is caused by skin allergies in dogs.
This will remove any allergens or as much as possible from their coat and skin.
If your itchy Golden has scratched so much that they are starting to lose fur and their skin looks really red they may have a secondary bacterial infection. If your Golden Retriever has skin lesions wash very gently around those. Simply put dandruff is a. If it is not doing it due to an injury and it is healthy it would also help to give it daily exercise.