Hello frnds m gaurav Gupta and m sharing experience most of the skin soaps we use today contain caustic soda, which causes very damage to skin. Caustic soda is so powerful that it can eat away paint on the surface to metal.Generally, caustic soda is used to clean the old paint on metals of car and other vehicles while repainting.
You can observe this yourself. After bathing with soap, let your skin get dried. Then just scratch your skin with you nail you can observe a while layer on your skin. This is just because of caustic soda uSed in making of skin soaps
Thank you