Hmmmm....at first I thought this post was entitled, "When to GO NUTS" and I thought I might be able to give some tips....ha ha ha.
About giving nuts--I think you probably should consult an allergy specialist before you attempt that with your son if he is really allergic. There are some prior tests they can give him to determine if he is allergic to them. That's probably safer than trying to give him nuts and then facing an emergency if he has a terrible reaction. If you are interested in a more holistic and homeopathic way to determining food allergy the Optimal Health Center in Causeway Bay offers a wide range of allergy testing with one blood draw. The information is here.