Irritant contact dermatitis typically starts on the areas of the body that come into direct contact with the irritant substance. The most commonly affected areas are the hands and fingers, as they are frequently exposed to various substances during daily activities. However, irritant contact dermatitis can also occur on other parts of the body that come into contact with irritants, such as the face, arms, and legs. The specific location may vary depending on the source of the irritation and individual circumstances.