If a drop of vitamin D has gotten into your baby's eye and their eye and eyelid are still red, it's best to call the Poison Control Center for quick advice. Vitamine D typically doesn't cause allergic reactions or toxicity to the mucous membranes, so the redness is likely due to simple inflammation. Keep an eye on the redness and visit a medical clinic if it persists. In the future, it's recommended to put the drop on the breast before breastfeeding or on a bottle nipple if the baby is bottle-fed.