In some medical cases, a severe "accident"—such as a seat-belt injury during a car crash—has caused trauma to the milk ducts in postpartum or pregnant women, leading to a massive collection of milk within the breast.

Stimulates the small sacs in the breast (alveoli) to take nutrients from the blood and turn them into milk.

Intense physical stress or chest wall irritation can sometimes trigger the pituitary gland to release prolactin , the hormone responsible for milk production.

While extremely rare, physical trauma to the chest can lead to , which is the production of breast milk unrelated to pregnancy or nursing.

Known as the "love hormone," it causes the muscles around the milk ducts to contract and push the milk out, a process called the let-down reflex .