Parenting: 3-Year-Olds Community

Hi mommies,

For the last month, on/off my little man has been coughing at night. Hacking, phlegmy coughs that scare the crap outta me. I live in NYC and the allergy season has absolutely been killer since the beginning of April, which is kinda when it started. It's one of the most frightening sounds I've heard, sometimes he coughs so hard he turns purple in the face. I've been to his doctor and to his ENT (he has tubes in his ears to clear the airways because he kept getting ear infections) and they both tell me it's simply allergies. But I've never heard of allergies causing coughing. Sneezing, yes, but coughing? Although to be fair he does get itchy eyes, but not all the time. And the building behind mine is doing constrution (I keep his window shut and they hung a tarp over the side of my building to try to keep the debris out).
Ok, I'm going to forewarn everyone, I'm pretty scared when it comes to my babies and their health. I try not to get too alarmed but these random things frighten me more than anything has ever in my lifetime. I don't know what to do. He's been good for the last few (except last night, he was coughing last night). I've given him Claritin, nothing, Benedryl, nothing. I finally tried Delsym and that works for the most part, but not always (i.e. last night it wore off).
I'm trying so hard not to jump to horrific conclusions, so here I am asking if my little man is the only one suffering through this. This isn't the first time these random spurts have occurred, but then he goes through these long stretches and then these happen again. I keep my cool real well but in my head I'm freaking out over this. Please, if anyone has any advice, or words to keep me calm I'd appreciate it. Since I've had my second I'm extra sensitive and I'm quicker to worry. I guess it's still the hormones (my second son is 5 months old).

Thanks in advance.