What are the possible causes of nipple discharge?

Several conditions can cause a leaking breast. Causes of harmless discharge include:

  • Hormone imbalances
  • Medications, including birth control pills and some antidepressants
  • Nipple stimulation or friction from clothing
  • Pregnancy or breastfeeding
  • Sexual arousal
  • Stress

Doctors consider nipple discharge abnormal when it occurs spontaneously (not caused by breast stimulation), is bloody, or only occurs in one breast. Conditions that may cause abnormal nipple discharge include:

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