Hives that just won’t go away? A vitamin deficiency could be to blame

Burning welts, relentless itching, sleepless nights spent scratching without knowing why. Anyone living with chronic spontaneous urticaria is all too familiar with this cycle of symptoms that strike suddenly, seemingly for no reason. But now an Indian study, carried out by researchers at All India Institute of Medical Sciences (Bibinagar, Hyderabad) and involving 57 adult patients treated at a dermatology department between September 2023 and August 2024, has turned the spotlight on a new suspect: vitamin B12 – or, more precisely, a deficiency of it.

The researchers analysed the link between levels of this vitamin – which is essential for the immune system and the functioning of the nervous system – and various disease parameters: the duration of the hives, the intensity of the itching, the presence of angioedema, urticaria activity scores and even the autoimmune component, assessed using an autologous serum skin test.

The most interesting finding concerns the duration of the wheals. In patients with vitamin B12 deficiency – defined as levels below 200 pg/mL – the wheals remained visible for an average of 120 minutes, twice as long as the 60 minutes observed in those with normal vitamin levels. This difference is statistically significant and is accompanied by a general negative correlation between B12 levels and the duration of skin manifestations: the lower the vitamin level, the longer the wheal persists. Itchiness also appears to follow the same pattern, with a tendency towards greater persistence in patients deficient in this vitamin, although in this case the result did not reach full statistical significance. The picture is different for other aspects of the disease: vitamin B12 was not found to be linked to the overall duration of the disease, the urticaria activity score, the presence of angioedema, positive autoimmune test results, or IgE levels.

In the sample studied, a genuine vitamin B12 deficiency was found in around 16 per cent of participants, whilst the vast majority had normal levels. The test for autoimmunity, on the other hand, proved positive in around one in five patients, a finding consistent with what is already known: autoimmune forms of chronic urticaria tend to be more severe and more resistant to traditional antihistamines. Why would a vitamin that is important for the proper functioning of the nervous system affect the skin? The study’s authors hypothesise several possible mechanisms. Vitamin B12 plays a role in regulating the immune system and in methionine metabolism; a deficiency could promote inflammation by increasing homocysteine levels in the blood or alter the immune pathways involved in the activation of mast cells, the cells responsible for urticarial wheals. However, these are ‘plausible’ biological hypotheses, but they have not been directly verified in this study.

Before rushing out to stock up on vitamin supplements, it is therefore worth bearing in mind the study’s limitations: the sample size is small, the research was conducted at a single centre, and the cross-sectional design does not allow for the establishment of a cause-and-effect relationship. Furthermore, there is a lack of information on diet, any use of supplements, smoking and alcohol consumption – all factors that may have influenced the results. Nevertheless, the authors suggest that vitamin B12 supplementation may be beneficial in patients with particularly severe, persistent or treatment-resistant chronic spontaneous urticaria, as part of a broader assessment. It remains to be seen, through future prospective studies, whether correcting any vitamin B12 deficiency actually leads to an improvement in symptoms: the way forward is open, but the final word still rests with research.