Thanks, Radgirl. We're definitely going to try and get our son retested, now that he's thinking about his future career and knowing that this problem could close certain options to him. We're hopeful he may be among the one in five children who grow out of the allergy, especially as he thinks he may have come into contact with the allergen with no ill effects, but we would need to have it medically confirmed.
To answer your question: he really did react to peanut butter as a toddler - he was covered in hives, but that's as far as it went. Then, when he was about seven, someone was handing out Celebrations chocolates at school and he managed to pick the Snickers one (
) and promptly came out in hives again and threw up. The hives and vomiting are early stages of anaphylaxis (subsequent attacks can be more severe) so he was an obvious candidate for testing with his sister, who has always been much more sensitive to the allergen. This was confirmed in the skin-prick test, when the blister that came up on her arm was much bigger than the one on her brother's (of course they had to compare them!!!) The tests were carried out at our local NHS hospital, so no real incentive for a positive result especially as the two of them now have to be kept stocked up with Epipens! I have two other children who are not affected at all, including a 20 year old who's at university and tucks into peanut butter ad infinitum now she's left home.