It's a common surprise for expats and long-term travelers: allergies that were mild or nonexistent back home suddenly flare up somewhere new. Pollen types, flowering seasons, and even air pollution levels vary significantly by region, and your immune system doesn't arrive pre-adjusted.
Why the trigger is different
Grass, tree, and weed pollens vary by species and region, and their seasons don't line up neatly with what you're used to. A country's spring can bring an entirely different set of allergens than the ones you've built up tolerance to over years.
Managing it day to day
Checking the local pollen forecast, keeping windows closed during peak pollen hours, and showering after being outdoors for extended periods all help reduce exposure. Standard antihistamines are widely available in most countries, though which ones require a prescription varies — worth checking locally rather than assuming.
When it's not allergies
New environments also mean new colds, new air quality issues, and occasionally new triggers you're not used to identifying. If symptoms include fever, facial pain, or don't improve with typical allergy treatment, it's worth having it checked rather than assuming it's pollen.