Changes in Skin Test Aeroallergen Sensitization in Mexico Over the Past 14 Years and According to Climate.

Introduction: Aeroallergen exposure has an intra- and extra-domiciliary component and varies according to climatological zones. Mexico is a large country with a great variety of climates. A previous study (2009) evaluated skin prick test results (SPT) in different regions. In this study, we compare previous sensitization patterns from 14y ago with current ones and compare them between different climatological zones.

Methods: Mexican allergists were asked to share their last 100 SPT results in patients with respiratory allergy. Clinics were grouped in (semi)humid vs (semi)dry zones. Results were analyzed nationwide and compared to the 2009 results, calculating odds ratio (OR) and 95% confidence intervals (95% CIs), with p <0.05 as cut-off. Similarly, we compared (semi)humid versus dry zones.

Results: We collected 2915 SPT results from 28 clinics (19 cities). Dermatophagoides was the most frequently sensitizing allergen. There was a significant increase in SPT positivity from 2009 to 2023 in both in- and outdoor aeroallergens (OR 1.26-2.65, 95% CI from 1.06-1.50 to 1.99-3.52). Comparing dry-humid zones, sensitization to pollen from Oleaceae, Fagaceae (p < 0.0001 all) and most weeds is more frequent in humid zones, as are Dermatophagoides and cockroach (both p < 0.0001). Eucalyptus, mesquite, and all grass pollen sensitizations predominate in dry zones (p < 0.05-0.0001). There are no differences in sensitization to cat or dog between zones.

Conclusion: We found a general increase in SPT sensitization over the past fourteen years, suggesting that this is probably not only due to climate change. The different sensitization profile throughout the country was mainly related to humidity. Repeating epidemiologic SPT studies over the years could help tracking changes in allergen sensitization over time.