Is it his allergies or what?

Okay so for the past 3 days my boyfriend has been congested, sneezing and coughing up phlegm. He weedeated a yard a a few days ago and he thinks that's what caused it. Also, last night it was hard for him to fall asleep because his chest hurt so much because he said it felt like he had fluid in his lungs. So is it just his allergies or something worse?