Clinical and Etiopathological Perspective of Vitamin B1 Hypersensitivity and an Example of a Desensitization Protocol

Vitamin B1 (thiamine) is a water-soluble B vitamin. As a cofactor of many enzymes, it is essential for the proper functioning of many body systems and organs, including metabolic and energy metabolism. In extreme cases, vitamin B1 deficiency causes neurodegenerative disorders, including beri-beri, or cognitive impairment resulting from encephalopathy. B1 avitaminosis may result from increased demand, dietary errors, malabsorption, or excessive loss. Thiamine supplementation is used in cases of vitamin B1 deficiency or for preventative measures in situations of increased demand. Vitamin B1 can be administered enterally or parenterally (intravenously, intramuscularly, subcutaneously). The route and dose depend on the individual patient's clinical situation. Hypersensitivity to vitamin B1 is rare and appears to be primarily associated with rapid intravenous infusion of large doses of thiamine hydrochloride over a short period (intravenous bolus). Hypersensitivity to thiamine administered by routes other than intravenous or intramuscular injection appears to be an incidental phenomenon. Thiamine should also be considered as an occupational allergen. The mechanism of thiamine hypersensitivity has not been clearly elucidated. However, considering the clinical nature and dynamics of the reaction, the most likely reaction seems to be an immediate type of hypersensitivity reaction (immunoglobulin E (IgE)-dependent), in which thiamine (but not its metabolites) acts as a hapten. Diagnosing hypersensitivity to vitamin B1 is difficult due to the lack of validated tests for additional testing. In individuals requiring thiamine supplementation who have experienced hypersensitivity to intramuscular or intravenous administration of this vitamin, switching to oral administration may be considered (provided this does not reduce treatment efficacy). This form of supplementation is usually well tolerated by individuals allergic to parenteral thiamine. However, if enteral supplementation does not guarantee the maintenance of therapeutic potential, thiamine desensitization may be considered, which seems to be an effective therapeutic method in such a clinical situation.