A food diary is an excellent idea. Common culprits, as I'm sure you know, are dairy products, citrus, egg whites and certain grains.
If he hasn't seen a good pediatric allergist, I'd try to arrange that. Testing in young children is notoriously unreliable, but they do specialize in determining what items are suspect.
If you have pets in your home, consider keeping them outside the main living areas or at the very least out of your child's bedroom. Cover mattresses and pillows with occlusive covers (vinyl or the like). Wash bedclothes regularly. Try to buy stuffed toys that are washable, and also wash them regularly. For many asthmatic children, dust mites or animal danders are the culprit.
Please don't consider putting your child on paleo or any other highly special diet. Children's growth and brain development depend upon eating the right foods in the right amount, and restrictive diets can be harmful.
Finally, your instincts are right in wanting to get him off steroids as much as possible. Their long-term effects include growth retardation, eye and bone problems and many other non-reversible destructive changes. If you can get him to the point where steroids are used only in emergencies or when he's having extreme problems, that would be great.
Good luck, and let us know how he's doing.
Ulcerative colitis diagnosed in 2001; symptoms as early as 1992. In remission since 2006 with Remicade.
Inflammatory osteoarthritis; osteonecrosis from steroids
Grave's disease successfully treated with radioactive iodine and now on Levothyroxine.
Type II diabetes induced by steroids.
Meds: Remicade, Colazal, Levothyroxine, Mobic, Metformin
Moderator, thyroid forum