I'm not sure if you need to get him new medicine, but you may want to talk to his doctor about the reaction.

From my experience, my advice to you for now is to avoid any food that contains peanuts or may contain peanuts until you get a peanut allergy confirmation by a specialist. Read labels carefully. I would also warn the people around you that take care of your child to avoid giving him food with peanuts. See your pediatrician to discuss the symptoms and get a prescription for an epipen Jr. because the symptoms may become more severe the more the child is exposed to the allergen. You don't want to take chances. The oral allergy medicine you give may not have immediate effects whereas the epipen will. I had to use it once on my daughter because the oral medicine I gave her didn't have effect. Anaphylaxis shock is not only about breathing problems, it's also severe hives and/or severe swelling. Book an appointment with an allergy specialist to get him tested for peanut allergy.
I have 3 kids (3 to 9 yrs old) with severe food allergies (peanuts, treenuts, crustaceans, dairy, eggs, kiwi)and the symptoms are different from one child to another (hives, swelling, asthma, fainting). The 3 of them have epipens and they all have been tested by an allergy specialist to confirm their multiple allergies.
good luck!