Complications of Vitamin B12 Therapy
While cobalamin demonstrates promise in the treatment of certain dermatologic conditions, it is already in widespread use to treat cobalamin deficiency. It is important for the dermatologist to recognize various dermatologic adverse effects that can complicate therapy with cobalamin. There have been several reports of monomorphic acneiform eruptions in patients treated with intramuscular cobalamin injections. The eruptions resolved after cessation of the therapy. Cyanocobalamin, pyridoxine (B6), and riboflavin (B2) have been reported to exacerbate existing acne. Supra-therapeutic doses of oral vitamin B12 and B6 at 4,000 and 2,000 % the recommended daily allowance, respectively, resulted in the onset of rosacea fulminans in a 17-year-old female. Allergic and anaphylactic reactions have also been reported in association with intramuscular as well as parenteral cobalamin. These are more common with cyanocobalamin, but have occurred with both of the available formulations, cyanocobalamin and hydroxycobalamin, with some patients showing crossreactivity to both.[40,41] In patients only sensitized to cyanocobalamin, changing to hydroxycobalamin is an acceptable treatment. In one case of a patient sensitized to both formulations, Kartal et al. were able to desensitize the patient to cyanocobalamin.
Since cobalt is a component of cobalamin, sensitivity to cobalt may cause problems in patients receiving vitamin B12 replacement therapy. In patients with allergic contact dermatitis to cobalt undergoing oral cobalamin replacement, several cutaneous reactions have been reported, including chronic vesicular hand dermatitis, cheilitis, and stomatitis. Erythematous, pruritic injection site reactions can occur with vitamin B12 injections. Foods naturally containing cobalt in the form of cobalamin have not been associated with systemic contact dermatitis due to the very small amount of cobalt. However, foods containing high amounts of cobalt in other forms have been shown to flare dyshidrotic eczema in some patients, regardless of patch test results. Stuckertand Nedorost proposed a point-based system for patients to reduce their intake of dietary cobalt. Of note, the amount of cobalt in dental implants is increasing and can cause oral hypersensitivity manifesting as a severe burning sensation in the mouth. Cobalt sensitivity is often associated with nickel sensitivity, and asking about nickel allergies may be helpful before starting vitamin B12 therapy. Spot tests for detecting cobalt are commercially available and are important in assessing skin exposure and health risks associated with metal exposures (e.g. https://www.smartpractice.com).
Am J Clin Dermatol. 2015;16(1):27-33. © 2015 Adis Springer International Publishing AG