Psoriasis
Living in moist humid climate appears to delay the condition for appearing.  Dry arid climates seem to aggravate the condition.  Washing your hands has a drying affect, which triggers the condition.  When washing, water removes oils from our body, and has a drying effect on our hands.  Washing with Psoriasis removes the dry skin, but then the skin underneath is raw.  Hard water appears to worsen the condition in dry climates, but not as much in humid areas.  Soft water appears better.