Wikipedia
Chhaupadi is a social tradition in the western part of Nepal for Hindu women which prohibits a woman from participating in normal family activities during menstruation because they are considered impure. The women are kept out of the house and have to live in a shed. This lasts between ten and eleven days when an adolescent girl has her first period; thereafter, the duration is between four and seven days each month. Childbirth also results in a ten to eleven-day confinement.
During this time, women are forbidden to touch men or even to enter the courtyard of their own homes. They are barred from consuming milk, yogurt, butter, meat, and other nutritious foods, for fear they will forever mar those goods. The women must survive on a diet of dry foods, salt, and rice. They cannot use warm blankets, and are allowed only a small rug; most commonly, this is made of jute (also known as burlap). They are also restricted from going to school or performing their daily functions like taking a bath, forced to stay in the conditions of the shed.
This system comes from the superstition of impurity during the menstruation period. In this superstitious logic, if a menstruating woman touches a tree it will never again bear fruit; if she consumes milk the cow will not give any more milk; if she reads a book about Saraswati, the goddess of education, she will become angry; if she touches a man, he will be ill.
Chhaupadi was outlawed by the Supreme Court of Nepal in 2005, but the tradition has been slow to change.