Allergy to Vitamin B-12

Vitamin B-12 is taken in supplement form for people who lack the essential vitamin. An allergy to vitamin B-12 is uncommon but is possible. states that B-12 is important for cell reproduction, growth and blood formation. If you have a known allergy to cobalt or if you've been diagnosed with Leber's disease, you should not take a B-12 supplement. If you develop adverse reactions after you ingest a vitamin B-12 supplement, call your doctor for an evaluation of your symptoms. Some reactions may be side effects rather than related to an allergy.

Vitamin tablets on a table.
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Allergic Reactions

To adequately diagnose an allergy, your doctor may recommend allergy tests to determine if your body creates certain antibodies, called immunoglobulin E, or IgE, according to the American Academy of Allergy, Asthma and Immunology. When you ingest the supplement, your body mistakes it as a dangerous substance and begins to defend against it with antibodies. Your immune system overreacts to the supplement and creates IgE antibodies that fight off the vitamin, resulting in the production of histamine. Histamine is a chemical in the body that causes inflammation in soft tissue, leading to most allergy symptoms.

Signs and Symptoms

A vitamin allergy will cause mild to severe symptoms shortly after consuming the supplement. Common signs and symptoms include headaches, itchiness, asthma, general fatigue, runny nose, skin rash, wheezing, sniffling and sneezing. You may also develop digestive complications, such as nausea, vomiting, diarrhea, cramping, gas and stomach pain. More severe symptoms include hives, difficulty breathing and swelling in the face, lips or tongue, according to Call your doctor if you develop any of these signs or symptoms. A severe allergic reaction may lead to life-threatening anaphylaxis.

Side Effects Vs. Allergic Reaction

Signs and symptoms may not be related to an allergic reaction. states that common side effects from taking vitamin B-12 include chest pain, unusual warmth in the arms or legs, rapid weight gain, headache, weakness, dizziness, numbness, nausea, diarrhea, pain, swelling, redness, fever and upset stomach. To confirm a vitamin B-12 allergy, your doctor may perform a skin prick test to determine if your body creates IgE antibodies after being exposed to the suspected allergen.


The most effective treatment for a vitamin B-12 allergy is to avoid consuming the vitamin. Your doctor may recommend incorporating foods that contain B-12 to avoid the need for a supplement.

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