Why some products irritate your skin and some not

This website has helped me a lot. One curiosity: I thought the brand L’Occitane de Provance was a very delicate brand for people with sensitive skin. When I read this brand on your web, most products are “irritancy high. “ I don’t understand all the ingredients, but I think it makes those products irritable combinations of chemicals ingredients. Can you give me some information about what some products irritate your skin, and some do not? I appreciate the answer. This area is exciting. Thanks for helping me a lot.