I live in a hard water area, and I sometimes get very itchy skin (typically on my arms and legs) that feels like having tiny pin-pricks, after taking a shower. It lasts for ten minutes or so, then goes away. I don't use any shower gel, soap or shampoo, so its pure tap water. I'm male, and I have hairy arms and legs. Could it be the hairs reacting to the change in temperature?