Was your Dog outside before this happened?
Have you changed food or any thing you clean with in the house?
Is this the first time this has happened?
Dogs and cats seem to have immunity to the toxins in Poison Oak, Ivy and Sumac, however you can get it if they have in contact with those plants, because they can bring it in on their coats: http://vetmedicine.about.com/od/toxicology/f/Do-Dogs-And-Cats-Get-Poison-Ivy.htm
What you are describing sounds like a seasonal allergy. Unfortunately, allergens can be airborne, inhaled, ingested or contact. The red bumps you are describing becomes a bacterial skin infection called a pyoderma and may be caused by one of the allergens mentioned. You can try bathing your boy in a an Oatmeal bath with a little baking soda to relieve the itching. To stop the itching and give some relief Plain Benedryl can give some immediate both internally and topically. This is a link on Benedryl http://www.petplace.com/drug-library/diphenhydramine-benadryl/page1.aspx This can be given 1-2 mgs per pound of body weight every 8-12 hours to help clear the allergic reaction.
If the Benadryl does not stop the itching, you may have to see your Vet tomorrow for a shot that is more long acting to help relieve the problem. During the summer months we see this quite often and some dogs are more susceptible to allergic reactions than others. Joan