Peanuts is one of the more common allergy-causing foods. Peanuts are not actually a true nut they are a legume (the same family as peas and lentils), but the proteins in peanuts are similar in structure to those in tree nuts so people who are allergic to peanuts can also be allergic to tree nuts, such as almonds, Brazil nuts, walnuts, hazelnuts, macadamias, pistachios, pecans, and cashews.
It is probably best avoiding nuts altogether unless you definitely know for sure that you can eat them with no problems.
Hope this is of help.
Two completely speculative answers:
It may not have been the peanuts he was allergic to. Sometimes machines that process peanuts also process other foods such as tree nuts.
Either the peanuts themselves or the handling of peanuts could have given him a food borne illness. Sometimes these things look similar.
It ought to be easy to test to see if he really have a peanut allergy. If that test is negative, then its one of these other explanations.
He may very well develop a sudden allergy to peanuts.
It comes down to an abnormal immune response to over exposure (one food trigger too many).
Peanuts is one of the most common allergies and also one of the deadliest.
As said above, he needs to follow through with allergy testing.
Please carry an epi pen at all times .... having a reaction like that from whatever caused it is called anaphylaxis and once it progresses can quickly lead to death and cannot be reversed after a certain point. Actually 2 epi pens are recommended because the first one only lasts 20mins.
My daughter is analphylactic to latex, plums, and certain nuts. She tested bloodtest RAST very Positive to many nuts as well as the latex and plums and has had reactions.
Similar to what Swampcritter mentions, my daughter ate a peach gummy ring candy and had her throat start to close with severe stridor within 30 secs .. the container said it was cross-run on equipment that also produces nuts. She was ok after a trip to the ER where we learned we should have injected the Epi Pen.
Please let us know how he makes out at an allergist ... they will be able to help you learn what to do and not do but at all cost, do not eat nuts and be very careful reading labels.
I have nut/milk allergies. have you had blood/skin testing at an allergist? you can get allergy shots from a doctor
since your allergy is severe I would be really careful and read all food labels and even avoid the foods that were processed on machines that processed nuts
can you get wheezing and swollen throat from a nut allergy? I can't figure out why I am wheezing for 12 weeks now