V. I get this all the time if I don't wear a nose plug in the water. It doesn't seem to matter much if I'm in the pool or out for an OWS. If I screw up and don't have a nose plug, I have to take a claritin to make it through the night. Prior to using the nose plug I used to take a claritin about 30 min before getting in the water and that worked too. Eventually I went to the nose plug because I was tired of taking the meds. It took a while to get used to the change in breathing but ultimately it worked much better.

I haven't had the jaw thing to go with it though.