evidence: The injectable form of vitamin K can rarely cause severe (sometimes fatal) allergic reactions when given by injection into a muscle or vein. Vitamin K should be injected into a muscle or vein only when it cannot be given by injection under the skin or taken by mouth, or when your doctor has judged that the benefit is greater than the risk. Get medical help right away if you experience symptoms of an allergic reaction such as rash, itching, swelling, dizziness, or trouble breathing. Before using vitamin K, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details. [...] Vitamin K passes into breast milk, but is unlikely to harm a nursing infant. Consult your doctor before breastfeeding.