Vitamin B12 is commonly injected by a medical doctor to treat conditions such as pernicious anemia, according to Drugs.com. Although uncommon, you may experience an allergic reaction to the injection. You can also develop allergy symptoms within a few minutes of taking vitamin B12 orally. Before using any dietary supplement, talk with your doctor.
Symptoms
Symptoms can appear minutes after taking an oral supplement or receiving an injection, although it may take a few rounds of receiving the supplement before symptoms develop. Common symptoms include skin rashes, hives, eczema, itchy skin, inflammation at the site of injection, redness, shortness of breath, wheezing, chest tightness, nasal congestion, runny nose, sneezing, watery eyes, nausea, vomiting, diarrhea, stomach cramping and abdominal pain, according to Health Tree. Call your doctor at the first sign of any allergy-related symptoms.
The Cause
An allergic reaction to a vitamin B12 supplement is a hypersensitivity to the substance. The body doesn't recognize the supplement and begins to defend itself. The immune system quickly responds and begins creating specific antibodies to fight off the compound, according to MedlinePlus. Antibodies are disease-fighting agents in the body that typically ward off bacterial and viral infection. These antibodies, together with the effects of histamine released during the immune response, cause a cascade of effects that lead to an allergic reaction.
Severe Reactions
Drugs.com reports that cases of severe allergic reaction to vitamin B12 injections have occurred. A severe allergic reaction, or anaphylaxis, is a life-threatening condition that requires immediate medical attention. Symptoms of anaphylaxis include feeling faint, increased heart rate, the inability to breathe, skin turning blue and facial swelling, according to MedlinePlus. If you experience these symptoms, call 911.
Diagnosis
If you have an adverse reaction after receiving vitamin B12, your doctor may recommend allergy testing. Not all reactions are related to an allergy, and it may be necessary to determine whether your body is creating IgE antibodies, or immunoglobulin E, a type of antibody specific to an allergic reaction. Your doctor may perform a blood test or skin prick test to determine if your body is creating IgE antibodies when vitamin B12 is introduced.
Treatment
The most effective treatment for an allergic reaction is to remove and avoid exposure to the allergen, according to MedlinePlus. Your doctor may recommend stopping vitamin B12 therapy and recommend another treatment option. A severe allergic reaction requires an injection of epinephrine to prevent further complications.
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