What Causes Itching Sensation In Skin After Coming In Contact With Rain Water?

Hi, my name is Azaria and I am thirteen years old. Although it is only tropical rain that does this, but when my skin comes into contact with tropical rain, I start to itch real bad. I itch everywhere, whether it s on my legs, hands, arms, or neck I go ballistic and think of nothing else except scratching the itch. I found this out during a trip to Cancun, Mexico when I was twelve. Also, when my mother was younger and lived in Sierra Leone, Africa, she had the same problem but then grew out of it when she grew older. What is making my skin itch?