Vitamin B12, also marketed as cyanocobalamin is a water-soluble B-complex vitamin that is involved in DNA synthesis, production of healthy red blood cells and the maintenance of a healthy immune system. Animal foods such as milk, red meat, shellfish and eggs contain vitamin B12. Deficiency in vitamin B12 causes pernicious anemia and nerve damage and is treated using vitamin B12 supplements. Patients allergic to ingredients in vitamin B12 supplements may develop rash symptoms.
Hives
Patients allergic to vitamin B12 supplements may develop hives, which appear as swollen, red itchy bumps or wheals, according to Drugs.com. Hives of various sizes appear anywhere on the body and may join together to form larger areas known as plaques. Patients who develop hives and have trouble breathing after taking vitamin B12 supplements should discontinue the supplement and go the emergency room immediately.
Red and Itchy Rash
Patients with drug allergies may experience a red and itchy rash after taking vitamin B12, according to Drugs.com. The rash may also be scaly, crusty or blistered. Vitamin B12 causes an allergic reaction in such patients. Patients who experience these symptoms and difficulties breathing should stop taking vitamin B12 and seek immediate medical attention.
Rosacea
Patients may develop a rash known as rosacea after taking vitamin B12. Patients with rosacea have a flushed appearance with redness around cheeks, forehead, chin and nose. Symptoms of rosacea are more common in patients who ingest more than 100 mcg of vitamin B12, according to Drugs.com. Rosacea usually resolves after vitamin B12 is discontinued.
