Hi
Welcome to the MedHelp forum!
CPAP machine can cause watery eyes, allergic reaction, sneezing, air in the stomach-gas and bloating. You can try a cold water humidifier to start with. If you want a raised head then the head end of the bed should be raised. Pillows should be kept to the minimum. Lowering the CPAP pressure can help but do not do this without consulting your sleep specialist. Switching over to bilevel pressure or C-Flex may help you too. So ask your specialist about it. Take care!
My husband has sleep apnea as well. I know sometimes his mask collects moisture and can cause some coughing but nothing like what you are experiencing. Have they tested him for acid reflux? That could be the culprit. Otherwise I would change the mask type he has and go fromthere. We had to change about 3 mask types before he found one that was compatible.