Hi I Am From Canada, And Every Single Time I

Hi

I am from Canada, and every single time I travel to the Caribbean my forehead starts to swell. The first time it happened it got so bad they hooked me up to IV for a couple of days, I was unrecognizable. The second time I went down south I noticed it happening again but caught it in time. I took some Benadryl and put on a cap. My hair is faily thin so I was thinking maybe the direct sun on my scalp may be the cause, but really unsure. Also both times it happened it starts the day after we went snorcling, so then I was thinking it's from their masks. Cause it's all around my face and forehead where the masks sits. Any suggestions?