If allergies occur during breastfeeding, stop breastfeeding. This is because anti-allergy medications may need to be taken during an allergy, and if breastfeeding is continued, the medication may enter the fetus through the milk, which can have an adverse effect on the baby. Only after the allergy has passed and the condition has improved can you continue to start breastfeeding. During the period of allergy, infant formula can be used instead of breast milk, and allergen tests can also be done to clarify what substances the baby is allergic to. If the allergens are clarified, you can prevent the next allergy from affecting breastfeeding.