Environmental Causes of Itchy Skin
1. Dry Skin
Dry skin (xerosis, winter itch) is common, especially in old people, and may be caused by cold weather, wind, sunburns, prolonged water exposure, frequent hot baths and using soaps (also washing powder and house cleansers) that can thin the protective oil layer on the skin and thus enable losing water through the skin.
2. Sweating
Microbes from normal skin flora break down the sweat (especially in armpits and groin) and yield substances that cause itching. Excessive sweating can be observed in persons with primary hyperhidrosis (increased activity of sympathetic nerves, possibly caused (but not confirmed) by psychological reasons), or secondary hyperhidrosis (e.g. in elevated thyroxine, tuberculosis, malignancies).
