A short distance south of the Church of the Nativity in Bethlehem is a shrine called the Milk Grotto, on a street of the same name.
An irregular grotto hollowed out of soft white rock, the site is sacred to Christian and Muslim pilgrims alike. It is especially frequented by new mothers and women who are trying to conceive.
According to tradition, while Mary and Joseph were fleeing Herod’s soldiers on their way to Egypt, they stopped in this cave while Mary nursed the baby Jesus. A drop of Mary’s milk fell upon the stone and it turned white.
The grotto has been a site of veneration since the 4th century, the first structure being built over it around AD 385. - Milk Grotto
As for the relics of the Passion of Our Lord Jesus Christ, the Catholic Church believes that they do exist and that she is in possession of such relics.
THE CROWN OF THORNS
By mixing the soft white chalk with their food, and praying to Our Lady of the Milk, they believe it will increase the quantity of their milk or enable them to become pregnant.
Rows of framed letters and baby pictures sent from around the world to the Milk Grotto testify to the effectiveness of the “milk powder” and prayer. (The powder is available only at the shrine; it may not be ordered from overseas.)
As for the relics of the Passion of Our Lord Jesus Christ, the Catholic Church believes that they do exist and that she is in possession of such relics: