Hi there. Am I correct in thinking that your son hasnt started his application process yet? If not, I would speak with the AFCO office first. They are very informative, so maybe try them. If you son had an inhaler when he was a baby as long as your medical record doesnt show any repeat prescriptions etc on the inhaler or anything on his medical records showing recent 'wheeze' or asthmatic symptoms, he should be OK. My doctor was happy to totally remove the word 'asthma' from my daughters records as previous tests proved she didnt have any astmatic symptoms and that in his opinion, she had only had a nasty cough following a cold. But with persistance, we got there in the end.
Keep me posted and of course, do what I did and get as much advise from people on this forum. We have found it brilliant.