It lasts more than a few hours, so I'm wondering if there is anything I can do to prevent it or relieve it. He already takes Zyrtec and Singulair for allergies/asthma. He swam a little bit yesterday and this morning he was all closed up and couldn't breathe through his nose. I gave him some Benadryl but it didn't do much for him. Does anyone else get this and is there anything that would help? Noseplug maybe?