Causes & triggers
Allergic rhinitis happens when the immune system overreacts to airborne particles. Knowing your specific triggers is the single most powerful step towards control.
The usual suspects: outdoor allergens
Tree pollen
Spring, before most leaves appear. Birch, oak, cedar, olive and alder are common culprits.
Grass pollen
Late spring to mid-summer, especially on warm, dry, windy days.
Weed pollen
Late summer and autumn. Ragweed is the big one in North America; mugwort matters in Europe.
The usual suspects: indoor allergens
Dust mites
Microscopic mites in bedding, mattresses and carpets. Their droppings are the actual allergen — and the bedroom is ground zero.
Pet dander
Skin flakes, saliva and urine from cats and dogs. Dander is light and stays airborne long after the pet has left the room.
Mould & damp
Mould spores thrive in bathrooms, kitchens, basements and anywhere damp. Some moulds are also outdoor seasonal allergens.
Cockroach allergens
A major indoor trigger in urban environments — found in droppings, saliva and body parts, often where food is stored.
Household dust
A mixture of everything above plus fibres and particles — the "catch-all" indoor trigger.
Not everything that bothers you is an allergen
Several non-allergic factors irritate the nasal lining and make allergic symptoms worse, even though they do not cause the allergy itself:
- Cigarette smoke — one of the strongest aggravators, indoor or outdoor.
- Air pollution — traffic fumes and fine particles increase sensitivity to allergens.
- Cold, dry air — weather shifts can trigger symptoms even without allergen exposure.
- Strong odours — perfume, scented cleaning products and paint fumes.
- Spicy food, alcohol, stress and some medicines — all can dilate nasal blood vessels and add to congestion.
Why some people and not others?
Allergy risk is a mix of genetics and environment. A family history of allergies, eczema or asthma raises your odds. But the environment matters too: urban air pollution makes people more sensitive to allergens, and early-life exposures shape the immune system. Nobody chooses to have allergies — it is not about lifestyle or hygiene.
Climate change is lengthening the allergy season. Across the Northern Hemisphere, pollen seasons now start about 10–40 days earlier and last around 20 days longer on average than three decades ago, with more pollen produced overall. Ragweed season above 44°N has extended by up to 27 days since 1995. For anyone with seasonal rhinitis, that means more weeks of symptoms every year — and more reason to plan ahead.
Find your triggers, not just the general list. Skin prick or blood tests can identify exactly what you react to. Until then, our trigger finder turns your exposures into a personalised avoidance plan.