Longitudinal Analysis of Seasonal Variations in Intradermal Test Reactivity and Serum Allergen-Specific...

In dogs with atopic dermatitis (AD), allergen testing is often timed to pollen exposure. However, data on seasonal effects on intradermal testing (IDT) and allergen-specific immunoglobulin (Ig)E serology (SAT) are limited.

To evaluate the seasonal effects on IDT and SAT results in dogs with AD by comparing aeroallergen test positivity across four seasons within the same cohort.

Twenty-six client-owned dogs with nonseasonal AD (six) and AD with seasonal pattern (20).

In this prospective longitudinal study, dogs underwent repeated IDT and SAT using two commercial assays during spring, summer, autumn and winter. Seasonal differences in overall and allergen group-specific positivity were analysed using nonparametric statistics and mixed-effects and generalised estimating equation models.

There was modest seasonal variation in overall (p = 0.004) and pollen-specific reactions (p = 0.005) on IDT, with autumn having the highest positivity rates. This pattern was seen only in dogs with a seasonal component to their AD (p = 0.007). Grass and weed allergens had higher odds of testing positive in autumn (odds ratio [OR] = 2.696, p = 0.032 and OR = 2.026, p = 0.034, respectively), while other allergens showed no consistent seasonal differences. No significant seasonal differences were detected in SAT, although subtle effects could have been missed owing to the sample size and conservative statistical adjustments. Disease duration did not influence seasonal testing patterns.

These findings suggest that, until further data are available, allergen testing in dogs, especially those with seasonal AD, may be optimally timed later in the season (autumn) to increase the likelihood of positive results.