Question

why doed ordinary soap cause irritation to skin?

Answer 1

Soap causes irritation primarily by drying the skin. Individual ingredients can also trigger irritation by causing rash and itching in those with skin allergies or sensitive skin. Because alcohol is drying, alcohol-based hand sanitizers are often implicated as a major cause of irritation, though this is not always the case. In soaps sodium lauryl sulphate is used which causes eye and scalp irritation and due to these chemicals and sometimes due to pH changes, soaps also cause irritation.