with people (especially children) i think a lot of it is psychosamatic,
many years ago we had friends who came to stay who's 7 yr old son was asthmatic and allergic to practically everything, he had the most terrible exma and was covered in sores, his face, knees, elbows, ankles............. almost on every part of his body his skin was cracked and bleeding, at night in his sleep he scratched and scratched and bled................ my mother nearly had a breakdown the first night she baby sat for him, she tried everything to keep his mind off the itchiness, the poor child was in agony,
after a few days he started to get better, we took him with us to the local show (giving his mum and dad a break) he had a great time, we took him on the pony rides and all the funfair games, when we got back home he was desperate to have a ride on our pony Noddy, so........... the next day i tacked up the long retired Noddy (my pony when i was little) and took him for a ride, he loved it, his breathing was fine, his skin was fine, he was fine, he cuddled Noddy and told him " i love you" it was hours later when his mother asked him what had he'd been doing that day and he told her, she screamed at me "you've had him near a pony?" when i told her he had ridden she went ballistic, she yelled at me that he was allergic to all animals and i had no buisness putting him at risk, at that exact moment he started to breathe funny, panting and gasping.....................
6 months later his mother died from a brain hemorrhage.............
2 years later his father remarried............
Simon's step mother was never told about Simon's allergies and she had many pets, i've been told he out grew his asthma and exma and is now perfectly normal,
i know a lot of people have genuine problems, but for that little boy he probably was allergic.............at the beginning ..........but his mother (in his best interests) i think kept him allergic..............