Can humidifier=worse cough?

I know there's very little we can do for a cough at this age, and the usual recommendation is to use a humidifier. We did that all winter during DS's various ear infections. Last month we quit using it as winter was ending and he was healthier. When he got sick again with yet another cold/cough, we started it again. That night, his coughing was so much worse. DH blamed the humidifier. I tried to explain that it is supposed to help. We didn't use it the next night, very little coughing.

Ok, so now DS has yet one more cold/cough, and had bad coughing fits in the night last night. I hadn't turned on the humidifier. I know the doctors all say that humidifiers help, but is there a chance that it could make it worse? I'm trying to decide if I should use it tonight but DH's pessimistic "doctor's don't know ***" attitude is starting to wear off on me. It's been a long winter with way too many colds/infections and we are so jaded. Yes, the humidifier is clean, I make sure of that. WDYT?