Vitamin B12 Injections Can Cause Acne Breakouts
Yes, there is clear evidence that vitamin B12 injections can trigger acneiform eruptions, though this is not listed as a common adverse effect in the FDA drug label.
The Evidence
The FDA drug label for intramuscular vitamin B12 lists dermatological adverse reactions as "itching" and "transitory exanthema" but does not specifically mention acne 1. However, multiple case reports and case series in the dermatology literature document this phenomenon clearly.
Clinical Characteristics of B12-Induced Acne
The acneiform eruption from vitamin B12 has distinctive features that differentiate it from typical acne vulgaris 2, 3, 4:
- Timing: Eruptions appear anywhere from 1 week to 5 months after starting B12 therapy (either intramuscular or oral)
- Morphology: Monomorphic papules and pustules (notably absent comedones and cysts)
- Distribution: Primarily affects the face, but can extend to neck, shoulders, chest, and upper back
- Pattern: Voluminous folliculitis lesions that develop acutely
- Resolution: Complete spontaneous remission occurs 3-6 weeks after discontinuing B12
Supporting Research
A 2018 case series reported five female patients (ages 21-62) who developed acneiform eruptions after B12 therapy 3. Histopathologic examination in one patient revealed eosinophilic folliculitis. Two patients had markedly elevated serum B12 levels. All cases resolved completely within 3-6 weeks of stopping B12.
The pathogenesis likely involves transcriptome changes in Propionibacterium acnes (now Cutibacterium acnes), the organism responsible for acne vulgaris 4, 5.
Clinical Management
If a patient develops acne after starting B12 injections, discontinue the B12 supplementation if medically feasible. The eruption will resolve spontaneously within 3-6 weeks 3, 4.
Important Caveats
Do not stop B12 in pernicious anemia patients without careful consideration: Patients with pernicious anemia require lifelong B12 supplementation to prevent irreversible neurological damage 1. If B12 cannot be discontinued, the acne may require treatment with standard acne therapies per guidelines 6.
Consider the indication: If B12 was given for simple dietary deficiency, oral supplementation may be substituted (though this may also cause acne in susceptible individuals) 3. If given for malabsorption, parenteral therapy is typically necessary 7.
Distinguish from drug-induced acne: The monomorphic pattern, absence of comedones, and unusual timing/distribution help differentiate B12-induced acne from acne vulgaris 2, 8.
When B12 Must Be Continued
If B12 therapy cannot be stopped (e.g., pernicious anemia, severe B12 deficiency with neurological symptoms), treat the acne according to standard guidelines with topical benzoyl peroxide, topical retinoids, or combination therapy 6. The acne may persist as long as B12 therapy continues.