Atopic dermatitis web searches track anomalous atmospheric humidity rather than chronic dryness: a bihemispheric infodemiological analysis

Atopic dermatitis (AD) is a chronic inflammatory skin disease triggered by gene-environment interactions. Researchers analyzed Google search volume for AD-related terms in 30 countries between January 2010 and March 2025. They found that search activity exhibited seasonality in 86.7% of countries (26 out of 30), with approximately 180-degree phase offset between hemispheres. Seasonality was strongest in mid-to-high latitude regions, including the United Kingdom, Russia, and Japan. Analysis showed that declining relative humidity and rising vapor pressure deficit were the most consistent correlates of increased search activity. Search activity responded to acute departures from local moisture norms rather than absolute dryness. Multivariable models improved explanatory power by 19.7 percentage points. The findings suggest that acute environmental desiccation, rather than chronic dryness, is the relevant triggering factor for AD.