It is great to get advice from others that have been there, but this is an amazing article by one of the leading integrative vets with very detailed information on solving seasonal allergies. Much of this can be applied to dealing with pit bulls. Pitties are particularly sensitive to food ingredients as well as environmental factors.
http://healthypets.mercola.com/sites/healthypets/archive/2013/07/01/pet-allergies.aspx
Ensure they are on a high-protein, grain-free, potato-free food like Orijen, LiveFree or Pioneer Naturals.
Use a combination of coconut oil and fish oil.
Regular rinse/bath/use foot soaks to eliminate pesky allergens.
Just like children with allergies, ensure that you do everything you can to eliminate environmental allergens in the home – clean air, air-friendly cleaners, and add diffusers.
