Vitamin B12 is an essential vitamin that the body needs for an efficient metabolism and the formation of red blood cells. While you may eat foods that naturally contain B12, such as meat, eggs, poultry, milk, shellfish and dairy products, you might experience an allergic reaction taking a B12 supplement. If you develop any adverse reactions while taking B12, stop using the vitamin supplement and call your doctor. Healthy adults typically don't need to take a B12 supplement because the body can store it for years in the liver.
Allergy
If you develop an allergic reaction after taking a B12 supplement, you'll develop distinctive symptoms that will need to be evaluated by your healthcare provider. The symptoms are the result of the immune system mistaking the foreign substance as an invader to the body that could cause harm, even though it is safe. The immune system immediately begins to defend the body by creating immunoglobulin E antibodies, or IgE. These antibodies are agents of the immune system that typically fight off infectious organisms that enter the body.
Symptoms
When the body creates IgE antibodies, mast cells throughout the body begin producing histamine, a chemical that helps fight against infection. During an allergic reaction, histamine is created in soft tissues throughout the body, resulting in increased inflammation. Swelling may occur in your lungs, digestive system, skin and sinuses, leading to symptoms that are common reactions to vitamin supplements. Common symptoms include diarrhea, vomiting, nausea, stomach pain, asthma, shortness of breathe, hives, facial swelling, eczema and nasal congestion.
Severe Reaction
In rare cases, you may develop a severe allergic reaction to the supplement. Anaphylaxis is an extreme allergic reaction throughout the entire body that causes your body to enter a state of shock. Common signs of anaphylaxis include the inability to breathe, dizziness, an increased heart rate, a sudden drop in blood pressure, pale-colored skin and a metallic taste in your mouth. These symptoms may be life-threatening. Call the 911 emergency hotline at the first sign of any of these symptoms because anaphylaxis forms quickly after the allergen has entered the body.
Testing
A diagnosis of your symptoms is required to avoid another allergic reaction. An allergist will expose your skin and blood to a small amount of vitamin B12 and observe your body to determine if you have a genuine allergy to B12 supplements. Not all adverse reactions are the result of an allergic reaction.
