Try putting some vicks on the bottom of his feet and then put socks on.
My son had that. They decided mild asthma. Hard for me to agree to that but I could only change his bedding in the middle of the night for so long before I gave in. Once I allowed him to have the puffers he was okay. Luckily he outgrew needing them by the time he was 7 yrs. I charted pollen counts (along with his symptoms) for a few years to see if there was a pattern. He was allergic to birch trees. Definitely worse with his coughing around their pollen time. The allergy disappeared at the same time as the asthma!! Woo hoo, I hope the same for you.