Sorry to hear about your son. It's really difficult because so many doctors in our area are not as experienced in food allergies as they need to be and the children are the ones who suffer. First of all, you really need to see a reputable allergist. I personally take my son to Children's Memorial, which is a two-plus hour drive each way for us, but it was SOOOOO worth it. They CAN and WILL do allergy testing on your son- a RAST test which is done with a blood draw (which they are VERY good at). If your son has a peanut allergy, they will prescribe and teach you how to use an Epi pen. All peanut allergies have the possibility of becoming fatal. They will give you all the education that you will need, like hidden or unsuspected places you might find peanuts (birdseed, pet feed, bean bags, etc.). My guess is that there is another allergen that your son is being exposed to because you don't know he is allergic to it yet. The top 10 allergens are peanut, tree nuts, milk, eggs, wheat/gluten, soy, fish, shellfish, dairy and seseme. They will probably test for all these and maybe a few others.
I know all of this information because we learned it the hard way. My son was very ill the first several months of his life, with excema that caused skin infections. We were told to seitch to soy formula and his vomiting got better but he still had the excema. We fed him peanut butter and he reacted with an asthma attack, hives and swelling of his face. We were told to give him Benedryl and watch him. (This, btw, could have killed my son. He was having an anaphalatic reaction which often can be fatal.) Since the excema never improved our peditrician tested him for wheat/gluten, dairy, dogs, and cats. He came out allergic to all of them. We had to give away our dog and his excema went away.
I was researching peanut allergy online one day and I came upon peanutallergy.com and started reading. I learned more information that day than a year of doctor's visits. I booked an appointment with Children's Memorial and my son has done extremely well ever since. They tested him and he came out alleric to peanuts (we were told to avoid tree nuts as well), egg, wheat, and dairy. We followed their instructions to the T. He has since outgrown hhis egg, wheat and dairy allergy. They gave us an Epi pen and told us how dangerous peanut allergy really is. We had NEVER been told the information that they gave us that day and I was furious that I was never made aware by local doctors. Really, I can't stress enough what a difference it made in my son's life to go to a REPUTABLE Children's Center. Please consider this because a peanut allergy is nothing to mess around with.
Good luck!!