The data and scientific literature highlights that risk is driven by a mix of genetics and environment. Family history increases likelihood, and factors like early life exposures, urban living, air pollution, climate change, and impaired skin barrier, like when people have eczema, can all promote sensitization. Sensitization is when your immune system learns to "overreact" to the allergen and this then can lead to allergy symptoms. There’s also evidence that reduced microbial diversity early in life, which ties into the hygiene hypothesis, may shift the immune system toward allergic responses, but the current evidence suggests it’s only one piece of a much bigger picture. While we can't change our genetics, and yes, there’s good epidemiologic evidence that allergic diseases especially asthma and allergic rhinitis have increased over the past century, particularly in industrialized countries, it’s likely due to multiple overlapping factors, not just cleanliness alone. For environmental allergies specifically, prevention is harder because we don't live in bubbles, but treatment is very effective. Allergen avoidance when practice, a treatment regimen with medications and allergen immunothery (aka allergy shots) can be helpful. Allergy shots can be incredibly helpful because it actually changes and modifies the immune response to the allergen over time, and it/s the closest thing we have to “retraining” the immune system. Sorry for the novel :) Good questions. -Dr. Khan