Final answer:
Periductal mastitis commonly affects lactating women due to the hormonal changes during pregnancy and breastfeeding.
Step-by-step explanation:
Periductal mastitis commonly affects lactating women. During lactation, milk moves from the alveoli through the lactiferous ducts to the nipples. Hormonal changes during pregnancy and breastfeeding stimulate the development and enlargement of the mammary tissue and the mammary glands.