Runny noses.

This may help. Ester C is better because it protects their stomach. You have to add it on a daily basis for it to work. Vitamin C is considered a powerful antihistamine. When a sensitive dog is exposed to an allergen, the immune system produces histamines. A dog's allergies can be managed with antihistamines. Studies have shown that dogs that consume higher amounts of vitamin C have fewer allergic reactions, and that vitamin C works like an antihistamine, inhibiting the production of histamines. If your pet is prone to allergies, a daily vitamin C tablet is recommended. The dosage should be adjusted according to the size and age of your pet. Give to bowel tolerance (for a small dog, start with 1/8 tsp twice a day and slowly increase until stools get a bit soft, then back down a bit. For a large dog, start with 1 tsp. twice a day).

Keep in mind that allergies are cumulative.  I discovered that my food allergies made my seasonal allergies much worse.  When I eliminated wheat from my diet, my seasonal allergies were tolerable.  I went from the strongest prescription antihistamines to seldom taking anything at all. 

Are your dogs on a grain-free diet?  Have you had the food allergy blood tests (controversial, but gives you a place to start)?