Allergy to Vitamin B12

People who are allergic to cobalt will have an allergic reaction to vitamin B12, also known as cobalamin. This is because cobalamin contains cobalt atoms. However, cobalt allergy and subsequent vitamin B12 allergy are rare.

Cobalt is a mineral with many uses. It's in rechargeable batteries, automotive airbags, steel-belted tires, and magnets. It gives a distinctive blue tint to glass and is used as a blue pigment in cosmetics, paints, and inks.

If you're allergic to cobalt, high vitamin B12 doses can cause contact dermatitis. This article explores the symptoms and causes of this allergy plus how it's diagnosed and treated.

Symptoms of Vitamin B12 Allergy

Taking large amounts of vitamin B12 can cause a skin reaction, called contact dermatitis, in people who are sensitive to cobalt. Contact dermatitis isn't usually life-threatening. However, vitamin B12 allergy can be life-threatening, but it rarely occurs.

Contact dermatitis comes in two types: irritant and allergic.

Irritants can cause irritant contact dermatitis in anyone, whereas allergic contact dermatitis is only possible if you're allergic to the substance.

A contact dermatitis rash is:

• Red, itchy, burning, and/or stinging
• Sometimes blistering or oozing
• Caused by direct contact with the problem substance

Your skin may be dry, cracked, inflamed, and tender to the touch. The reaction can happen anywhere on your body.

Prevalence of Contact Dermatitis

Contact dermatitis leads to millions of doctor visits each year in the United States. People of all ages are affected. Research suggests that 20% of all people are affected by this condition.

Females have it slightly more often than males. Teenagers and middle-aged adults seem to get it more than other age groups.

Causes

The allergy can be triggered by taking vitamin B12 supplements because B12 contains cobalt atoms.

Vitamin B12 supplements (either oral or injectable) are normally taken to support a healthy nervous system and are often needed in people who are deficient in vitamin B12. The deficiency can occur when people have difficulty absorbing foods with B12 in the small intestine.

Cobalt allergies most often develop in people exposed to it in eye makeup, tattoos, or industrial products, causing an itchy, red, scaly rash. Once you're sensitized to cobalt, you'll develop allergic contact dermatitis whenever you're exposed.

If you have a B12 deficiency, a cobalt allergy can make it hard to manage. Talk to your healthcare provider about how much B12 is safe for you.

Diagnosis

A cobalt allergy is diagnosed with a patch test. This involves placing a dime-sized cobalt-laden patch on your back for about 48 hours.

Your reaction is noted after 48 hours, then again a day or two later. The test is positive if you have blisters, redness, and/or mild swelling at the site.

A vitamin B12 sensitivity can appear as a rash after you take a supplement. A severe allergic reaction, known as anaphylaxis, can occur after taking large amounts of vitamin B12 orally or as an injection. 

Treatment

The rash from allergic contact dermatitis can be treated with topical or systemic corticosteroids. However, the best treatment for a cobalt allergy is avoiding large doses of vitamin B12 and products containing cobalt.

If you have a B12 deficiency, you should only take the minimum amount needed to raise your levels to normal.

Summary

Large doses of vitamin B12 can trigger a cobalt allergy. That may cause a red, painful rash called contact dermatitis. Most cobalt exposure is from makeup, industrial uses, and B12 supplements.

Cobalt allergies are diagnosed with a patch test. Contact dermatitis is treated with steroids. Avoiding large amounts of B12 and exposure to products containing cobalt helps manage the condition.