Plum’s Niacinamide Serum is generally considered safe for use during breastfeeding when applied topically in recommended amounts. Niacinamide is a gentle ingredient that is unlikely to pass into breast milk or harm your baby. However, since individual skin sensitivity and product formulations vary, it’s best to consult your doctor before using it. Always do a patch test and avoid applying it near the breast area to prevent accidental contact with your baby.