From the Research
Itchiness after a vitamin B12 injection is typically a mild allergic reaction that should be reported to your healthcare provider. To manage the itchiness, apply a cold compress to the injection site and take an over-the-counter antihistamine like diphenhydramine (Benadryl) 25-50mg or cetirizine (Zyrtec) 10mg to reduce itching, as suggested by recent studies on hypersensitivity reactions 1. If you experience more severe symptoms like difficulty breathing, facial swelling, or hives spreading across your body, seek emergency medical attention immediately as this could indicate anaphylaxis. For future B12 injections, your doctor might recommend pre-medicating with an antihistamine 30 minutes before the shot, switching to a different formulation of B12, or considering alternative administration routes such as oral supplements or nasal sprays. The itchiness occurs because your immune system is reacting to either the vitamin B12 itself or preservatives in the injection solution like benzyl alcohol or parabens. Most reactions are mild and resolve within a few hours to days, but it's essential to document this reaction for your medical records. Some studies have explored the effects of vitamin B12 in combination with other medications, such as diclofenac, for pain management, but these do not directly address the issue of itchiness after vitamin B12 injections 2. Older studies have investigated the impact of certain medications on vitamin B12 levels, but these are not directly relevant to the management of itchiness after vitamin B12 injections 3, 4. Given the potential for allergic reactions, it's crucial to prioritize the most recent and highest quality evidence when making recommendations, which in this case supports the use of antihistamines for managing mild allergic reactions like itchiness after vitamin B12 injections 1.