Riddle: You use it between your head and your toes, the more it works the thinner it grows. What is it?
This riddle here is not a difficult one. Even though its usage has decreased with the widespread use of shampoo and body wash, soaps have been used by people to clean themselves from head to foot for many years.
So, if you prefer to cleanse yourself with soap, you can use it for your whole body, and between your head and your toes. In addition, a soap naturally shrinks as you use it since it melts. Therefore, the more it works the thinner it grows.
The answer of this riddle is a bar of soap.