Many allergies are caused by excessive hygiene
Multiple epidemiological studies and reviews support the hygiene hypothesis, demonstrating that reduced microbial exposure and early-life disruptions to the microbiome (such as through antibiotic use) increase the risk of developing allergies.
The retrieved literature strongly supports the claim that reduced microbial exposure—often associated with modern hygiene practices and antibiotic usage—promotes the development of allergies. While some studies point to complex modifying factors (such as the specific type of animal exposure or demographic variables), the vast majority of relevant papers corroborate the core tenets of the hygiene hypothesis.
Helton C. Santiago, Thomas B. Nutman. Human Helminths and Allergic Disease: The Hygiene Hypothesis and Beyond. 2016. https://doi.org/10.4269/ajtmh.16-0348
Paper [0] discusses the hygiene hypothesis, explaining how a lack of early microbial and parasitic exposure alters immune development to favor allergic conditions.
Angela Pinot de Moira, N. Pearce, M. Pedersen, A. Nybo Andersen. The influence of early-life animal exposure on the risk of childhood atopic dermatitis, asthma and allergic rhinoconjunctivitis: findings from the Danish National Birth Cohort. 2023. https://doi.org/10.1093/ije/dyad040
Paper [2] reports that the overall associations between early-life animal exposure (a proxy for microbial richness) and allergic diseases were weak, suggesting the relationship is more nuanced.
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Z. C. Chiesa Fuxench, Nandita Mitra, Domenica Del Pozo, O. Hoffstad, Daniel B. Shin, S. Langan, I. Petersen, K. Bhate, David J Margolis. In utero or early in life exposure to antibiotics and the risk of childhood atopic dermatitis, a population-based cohort study. 2023. https://doi.org/10.1093/bjd/ljad428
Paper [1] shows that early-life antibiotic exposure, which disrupts the microbiome similarly to excessive hygiene, increases the risk of childhood atopic dermatitis.
Sheng Tai, Yi-Hsuan Lin, Ching-Heng Lin, Ming-Chih Lin. Antibiotic exposure during pregnancy increases risk for childhood atopic diseases: a nationwide cohort study. 2024. https://doi.org/10.1186/s40001-024-01793-9
Paper [3] finds that prenatal antibiotic exposure increases the risk of childhood atopic diseases in a dose-dependent manner.
S. Räty, Helena Ollila, Olli Turta, A. Pärtty, V. Peltola, H. Lagström, Johanna Lempainen, S. Rautava. Neonatal and early infancy antibiotic exposure is associated with childhood atopic dermatitis, wheeze and asthma. 2024. https://doi.org/10.1007/s00431-024-05775-1
Paper [4] links early infancy antibiotic use to higher rates of atopic dermatitis and asthma.
Huawei Zhao, Yijun Luo, Wenmi Li, Chenke Jiang, Endai Jin, Zhenghao Xu. Association between antibiotic exposure and childhood atopic dermatitis: a systematic review and meta-analysis. 2025. https://doi.org/10.1016/j.eclinm.2025.103296
Paper [5] provides a comprehensive meta-analysis confirming that early-life and prenatal antibiotic exposure significantly increases the risk of childhood atopic dermatitis.
Ya-An Tsai, Chen Yu Wang, Xiao-Ling Liu, Su‐Boon Yong, Jiu-Yao Wang. Hen’s Egg Allergy: Immunological Mechanisms, Epidemiology, and Predictors of Persistence in Childhood. 2026. https://doi.org/10.4168/aair.2026.18.3.339
Paper [8] notes that limited microbial exposure is one of the factors increasing the risk of allergic sensitization such as egg allergy.
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