People can sniffle plenty and not have the flu or another illness. Once you have become an adult, and pay attention, it is really easy to tell the difference. I frequently get allergic response to various things. Even when medicated, there is still a slow trickle.
Maybe you should trust people, he probably knows of if it is allergies or the flu more than you do.
I guess what you're saying makes sense. But some of those times, they complained about headaches and fever.
I mean, it is easy to spot when someone is actually sick vs. someone has allergies.
Regardless, in my country, it is not the "season" of allergies.