question about testing, any info helps :)
I am very new to this whole allergy thing.. a little back story if you're interested... or if you don't wanna read it all, I understand, just skip to the question 
No one in my entire family has any food allergies, nor does anyone in DH's so we know absolutely nothing... when our DS first turned one he had a bite of PB&J and started breaking out, acting lethargic and throwing up. I was so scared, I called his Pedi.. they told me to run to the pharmacy and get Benedryl.. we gave it to him and he was fine.. I've asked about it at subsequent pediatrician appointments and they just keep telling us to avoid giving him any peanut items until he is 2 when we can get him tested. At the same time, we noticed that if DH or I have peanut butter and, say, kiss DS on the cheek.. he will get a small rash where he have kissed him 
Obviously, since we noticed this we try our very best to keep anything peanut away from him.
My questions is, what/how do they test for allergies in a 2 year old? Is it a blood test or one of those "prick" tests? Can they tell you how severe the allergy is? His next appointment isn't until then so I want to be prepared.. can you think of any other questions/info I should know going into his 2 year check up?
thanks!!
Re: question about testing, any info helps :)
I agree with pp. You should see a pediatric allergist for testing now. They can do a blood test and a skin prick test. It will give you more info as to the severity of his allergy (and yes, what you have described is an allergic reaction). It's important to have him checked out because you may need to keep an Epipen on hand in case he ever has a severe reaction.
We first had DD1 tested for allergies at age 1 because she would get hives if dairy products touched her skin or if we touched dairy items and then touched her. She's allergic to dairy, soy, and eggs and her levels were high enough that we were prescribed Epipens.
DD1: allergic to eggs & dairy
c/p 4/1/11
DD2: milk and soy protein intolerant, allergic to eggs, soy, peanuts, tree nuts, sesame, bananas
MSPI Moms Check-In Blog
Our DS is the same way with peanuts. Our pedi immediately diagnosed it as an allergy after two exposures with allergic reaction results and gave us a prescription for an epipen! I would get a second opinion from a different pedi or an allergist. We have a peanut free house now.
Our pedi recommended us for allergy testing at a year. The allergist and the pedi said that there are more false positives for testing before a year. (We thought she had a pineapple allergy)
When we went at a year--we discovered she has a dog allergy and an egg allergy. I asked if they could test her for a peanut allergy--however the allergist said that if she never had peanut butter (and cross contamination doesn't count) than they really couldn't allergy test her. Apparently if there is no exposure--there is no allergens present and that could also lead to false positives.
The reason your doc wanted to wait is because food allergy tests (both the blood test and the skin prick test) have a high false positive rate. The reaction your child had (hives + vomiting +lethargic), any 2 of those and we use the EpiPen. A pedi-allergist would have probably given you an Epi that day.
Also, food allergies are not hereditary, but allergies are. So, if one of the parents has season allergies, environmental allergies, eczema, etc; then the child is more likely to have some sort of allergies, food allergies included.
I am pretty much repeating what everyone else has said, but I would definitely see an allergist. DS was almost 13 months when he had his reaction to peanut butter. Within a week we saw an allergist who prescribed him his Epi Pen Jr. His reaction sounds exactly what your LO went through.
His test was just the skin test - no "pricking" though, it didn't hurt him at all. The hardest part was waiting the 15 minutes for the skin test to be over, he didn't want to hold real still. We don't know how "severe" the allergy is, but they wanted a 3mm mark to indicate a positive allergy and his was 11mm.