Dermdoc 5% Glycolic Acid Under Arm Spray is generally considered safe to use during breastfeeding when applied only to small external areas such as the underarms. It has minimal absorption through the skin, so it is unlikely to pass into breast milk. Avoid applying it on or near the breast area and ensure the baby does not come into contact with treated skin. If you notice irritation or have sensitive skin, it is best to stop use and consult your doctor.