I got rashes when i shower, allergic to water?

No: Hot showers can dry the skin, or cause increased circulation to the skin, making the appearance of a rash. You are not allergic to water.

Yes: There is a condition known as aquagenic urticaria. The mechanism is unknown but some felt that it was induced by interaction of the water with sweat of the sufferers. This is not a common condition. A more common entity is cholinergic urticaria in which small red itchy hives erupt during the cooling down phase after a rise in core body temperature. This can be controlled with an antihistamine.