UK Hay Fever and Seasonal Allergy Guide

This is a comprehensive reference to the allergens that affect UK households, from grass and tree pollen to dust mites, pet dander and mould. For each allergen you will find its typical season, common symptoms, particle size and the practical steps that help reduce exposure. You will also find a clear explanation of how air filtration works, and why the difference between HEPA and MERV filter ratings matters when choosing an air purifier for allergy relief. It is written as general information to help you make informed decisions, and is not a substitute for advice from a pharmacist, GP or allergy specialist.

The UK allergen database at a glance

Allergic rhinitis and related conditions are among the most common long-term health issues in the UK. The table below summarises the main allergens covered in this guide, grouped by category, along with when they are most active.

Use the sections below to explore each category in more detail, including symptoms and the practical measures that make the biggest difference.

Pollen allergies (hay fever)

Hay fever, or seasonal allergic rhinitis, is triggered by pollen and affects more than 10 million UK adults. Because different plants release pollen at different times, the season stretches from early spring to late summer. Knowing your specific trigger helps you anticipate flare-ups.

Grass pollen

• Season: May to July, peaking in June
• Affects: Around 95 per cent of hay fever sufferers
• Symptoms: Sneezing, itchy eyes, runny nose and congestion
• Particle size: 20 to 40 microns

Tree pollen

• Season: March to May
• Affects: Around 25 per cent of hay fever sufferers
• Symptoms: Itchy throat, watery eyes and facial pressure
• Particle size: 15 to 30 microns

Weed pollen

• Season: June to September
• Affects: Around 15 per cent of hay fever sufferers
• Symptoms: Nasal congestion, itchy skin and headaches
• Particle size: Broadly similar to grass pollen

Dust mite allergy

Dust mites are one of the most common indoor triggers in the UK, affecting an estimated 12 million adults. These microscopic creatures thrive in warm, humid conditions and live in bedding, mattresses, carpets, curtains and upholstery. It is the protein in their droppings, rather than the mites themselves, that provokes an allergic reaction.

• Season: Year-round, often worst in autumn and winter when homes are warm and closed up
• Symptoms: Morning sneezing, a persistently stuffy nose, itchy eyes and coughing
• Particle size: 1 to 10 microns

Reducing dust mites

• Wash bedding weekly at 60 degrees Celsius to kill mites and remove allergens.
• Keep indoor humidity below about 50 per cent, since mites cannot survive in dry air.
• Use allergen-proof covers on mattresses and pillows.
• Choose hard flooring over carpet where possible, and vacuum regularly.
• Filter bedroom air overnight to capture airborne mite debris.

Pet dander allergy

Pet allergy affects an estimated 10 to 20 per cent of the UK population. The trigger is not fur but tiny proteins found in skin flakes (dander), saliva and urine. These particles are light and can stay airborne for hours, then settle into soft furnishings. Cat allergy is around twice as common as dog allergy in the UK.

• Season: Year-round
• Symptoms: Wheezing, skin rashes, itchy eyes and a runny nose
• Particle size: 0.5 to 10 microns, among the smallest common allergens

Managing pet allergens

• Keep pets out of bedrooms and off beds to protect the space where you sleep.
• Groom pets regularly, ideally outdoors and by someone without the allergy.
• Wash hands after handling pets and clean soft furnishings often.
• Because dander particles are so fine, air filtration is particularly valuable for this allergen.

Mould allergy

The UK's damp climate makes mould a widespread problem, and around 10 per cent of the population is sensitive to mould spores. Mould grows wherever there is moisture and poor ventilation, such as bathrooms, kitchens, basements and behind furniture on cold external walls.

• Season: Autumn and winter, and any prolonged damp period
• Symptoms: Coughing, wheezing, skin irritation and sinus problems
• Particle size: 2 to 10 microns

Controlling mould

• Ventilate damp rooms and use extractor fans when cooking or showering.
• Keep humidity below about 50 per cent and address any leaks or condensation promptly.
• Clean visible mould with appropriate products and dry surfaces thoroughly.
• Filter the air to capture spores that become airborne when mould is disturbed.

HEPA versus MERV: filter ratings explained

When comparing air purifiers, two rating systems come up most often: HEPA and MERV. Both describe how well a filter captures airborne particles, but they use different scales.

• HEPA (High Efficiency Particulate Air) is a standard requiring a filter to capture at least 99.97 per cent of particles at 0.3 microns, the hardest size to trap.
• MERV (Minimum Efficiency Reporting Value) runs from 1 to 20. Higher numbers capture smaller particles. MERV-13 is widely regarded as the practical sweet spot for allergen control, capturing fine particles in the 1 to 10 micron range while allowing strong airflow.

For everyday allergy relief, a well-designed MERV-13 system offers an excellent balance of capture efficiency, airflow and running cost. High airflow matters because a filter can only clean the air it actually moves through the room.

Choosing an air purifier for allergies

Its high clean air delivery means it can turn over the air in a typical bedroom several times an hour, while the low noise level makes it comfortable to leave running overnight, when uninterrupted filtration does the most to reduce morning symptoms.