Allergy to Vitamin B12

Allergic Contact Dermatitis to Cobalt and Vitamin B12 Allergy

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If you have a cobalt allergy, it may be triggered by vitamin B12 (cobalamin). That's because the cobalamin molecule contains a cobalt atom.

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. It's used as a blue pigment in cosmetics, paints, and inks.

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

Woman itching her arm.
GARO / Getty Images

Emergency Symptoms

In rare cases, intramuscular injections of vitamin B12 may lead to life-threatening anaphylaxis. Anaphylaxis is always a medical emergency.

Symptoms may include:

  • Itching
  • Hives
  • Shortness of breath
  • Wheezing
  • Vomiting
  • Diarrhea

Get immediate medical help for these symptoms.


Contact dermatitis isn't usually life-threatening. The rare vitamin B12 allergy can be. Even so, it's rarely reported.

Contact dermatitis comes in two types: irritant and allergic.

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

A contact dermatitis rash is:

  • Red, itchy, burning, and/or painful
  • 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.


Contact dermatitis leads to millions of doctor visits each year in the United States. People of all ages are affected. Research suggests 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.


A cobalt allergy can be triggered by vitamin B12. It can cause contact dermatitis, which is a painful, red rash. About one-fifth of Americans have contact dermatitis.


Vitamin B12 plays important roles in your body. It helps blood cells form. And it's critical for a healthy nervous system.

B12 is available in many dietary sources. Most multivitamins contain plenty, as well. Still, B12 deficiencies are common.

Vitamin B12 Deficiency

The National Institutes of Health says 6% of people under age 60 have a B12 deficiency. Among people over 60, it's closer to 20%.

Your body has to absorb vitamins in order to use them. With vitamin B12, the process is complicated. It includes various steps that are prone to defects.

That can lead to poor absorption of vitamin B12 from the small intestine. This causes a deficiency.

To raise your levels, you may need oral or injectable vitamin B12 supplements.

Cobalt and Vitamin B12 Allergy

Cobalt allergies most often develop in people exposed to it in eye makeup, tattoos, or industrial products.

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.


Most cobalt exposure is from makeup and industrial uses.

B12 deficiencies are common. A cobalt allergy makes them hard to treat.


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.


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

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


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 helps manage the condition.

A Word From Verywell

If you know you have a cobalt allergy, bring that up with any healthcare provider who suggests a B12 supplement. They can work with you to find a safe dosage.

If you have contact dermatitis or other allergy symptoms after a possible cobalt exposure, talk to your healthcare provider about allergy testing.

Any time you or someone else has trouble breathing, get emergency medical help.

Frequently Asked Questions

  • Can you be allergic to vitamin B12?

    Yes, people who are allergic to cobalt will have an allergic reaction to vitamin B12, also known as cobalamin. Cobalamin contains cobalt atoms. However, this allergy is rare.

  • Can too much vitamin B12 cause a rash or itchy skin?

    Yes, taking large amounts of vitamin 12 can cause a skin reaction in people who are sensitive to cobalt. The symptoms include an itchy rash. 

  • How do you know if you are allergic to B12 or cobalt?

    A cobalt allergy typically begins when you're exposed to cobalt in eye makeup, tattoos, or industrial products. It causes an itchy, red, scaly rash. 

    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. 

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Alinaghi F, Bennike NH, Egeberg A, Thyssen JP, Johansen JD. Prevalence of contact allergy in the general population: a systematic review and meta-analysis. Contact Derm. 2019;80(2):77-85. doi:10.1111/cod.13119

  2. Ullah MW, Amray A, Qaseem A, Siddiqui T, Naeem T. Anaphylactic reaction to cyanocobalamin: A case report. 2018;10(5):e2582. Published 2018 May 5. doi:10.7759/cureus.2582

  3. Brescoll J, Daveluy S. A review of vitamin B12 in dermatology. Am J Clin Dermatol. 2015;16(1):27-33. doi:10.1007/s40257-014-0107-3

  4. Langan RC, Goodbred AJ. Vitamin B12 deficiency: recognition and management. Am Fam Physician. 2017;96(6):384-389.

  5. Lidén C, Andersson N, Julander A, Matura M. Cobalt allergy: suitable test concentration, and concomitant reactivity to nickel and chromium. Contact Derm. 2016;74(6):360-7. doi:10.1111/cod.12568

Additional Reading
  • American Academy of Allergy, Asthma and Immunology; American College of Allergy, Asthma and Immunology. Contact dermatitis: a practice parameter [published correction appears in Ann Allergy Asthma Immunol. 2006 Dec;97(6):819. Beltrani, Vincent S [removed]; Bernstein, I Leonard [removed]; Cohen, David E [removed]; Fonacier, Luz [removed]]. Ann Allergy Asthma Immunol. 2006;97(3 Suppl 2):S1-S38.

By Daniel More, MD
Daniel More, MD, is a board-certified allergist and clinical immunologist. He is an assistant clinical professor at the University of California, San Francisco School of Medicine and currently practices at Central Coast Allergy and Asthma in Salinas, California.