The Role of the Hygiene Hypothesis in the Pathogenesis of Type 1 Diabetes

Type 1 diabetes (T1D) is an autoimmune disease where the immune system mistakenly attacks pancreatic β-cells, causing chronic inflammation and inefficient production of insulin due to decreasing βcell number. As insulin production declines, the body cannot maintain glucose homeostasis, leading to diabetes. The incidence of T1D has been rising during the last few years, along with the rapidly developing industrialized world. The hygiene hypothesis could explain this trend by suggesting that exposure to microbes in early ages functions to train the immune system. If the Immune system is highly trained, it is less likely to target self-antigens, reducing the risk of allergies and autoimmune diseases such as T1D. That being said, this review aims to evaluate how the hygiene hypothesis explains the pathogenesis of T1D. The analysis covers the theoretical basis and mechanisms of the hygiene hypothesis, early-life microbial exposures, gut microbiota diversity, environmental and geographical factors, trends in T1D incidence, animal models, and clinical trials. Evidence supports the hygiene hypothesis by highlighting the impact of environmental factors on immune development. However, current research produces contradictory results and often overlooks factors such as genetics, which also influence the onset of T1D. Future research should integrate genetics and other relevant fields with longitudinal data collection to further evaluate and refine the hygiene hypothesis.