at 3:23 PM on Sep. 20, 2010
It really just depends on how severe thier reaction to it is. It can also depend on the contact made with the allergen. Ex. my dd is severly allergic to peanuts...if she eats something with peanuts in it she will go into anaphylactic shock, if it just touches her skin and she does not ingest it she will swell up and break out in hives, if it is too close to her and she does not touch it she will break out in hives and usually starts coughing.
An allergic reaction can range anywhere from a runny nose to airways closing up. The only way to really tell is to introduce it to your child in a controlled environment such as getting an allergy test done.