Introduction

Asthma is a condition in which the airways temporarily narrow. People with asthma have twitchy airways that react to certain factors called triggers. These cause swelling and narrowing of the airways, leading to symptoms such as:

• Cough
• Chest tightness
• Wheeze
• Breathlessness

This guide explores a major asthma trigger—the house dust mite—and how to avoid it.

What Are Asthma Triggers?

Triggers are substances that provoke asthma attacks in those with asthma tendencies. They are:

• Lightweight, airborne particles
• Commonly found in the environment
• Often multiple in number for one individual

The House Dust

House dust is a mix of various particles. Components include:

• House dust mite allergens
• Animal dander
• Paper, wood particles, ash
• Insect fragments, skin flakes
• Cotton, wool, sugar, glass particles
• Plant pollen, fungal spores, paint chips
• Fingernail filings, food crumbs

The most significant trigger in house dust is the house dust mite.

The House Dust Mite

What Are They?

• Tiny, sightless, 8-legged arthropods
• ~0.3 mm in size (microscopic)
• Commonest species:
• Dermatophagoides pteronyssinus (European)
• Dermatophagoides farinae (American)
• Over 80% of asthmatics react to house dust mites.

Where Are They Found?

They thrive in:

• Beds and pillows
• Upholstered furniture
• Stuffed toys, carpets
• Areas with warmth, moisture, and skin flakes

A single mattress can contain 100,000 to 10 million mites.

How Dust Mites Trigger Asthma

It’s not the mites themselves, but:

• Their feces and dead body fragments
• These are protein-coated and airborne
• When inhaled, they trigger allergic reactions

Growth Conditions for Dust Mites

• Favor humidity and warmth
• Thrive in unclean, damp environments
• Die in dry, well-ventilated, hot spaces

Signs Your Asthma Is Triggered by Dust Mites

Ask yourself:

• Are symptoms worse in bed or on upholstered furniture?
• Do symptoms improve on holiday or in dry climates?
• Are symptoms worse when cleaning or in the morning?

Diagnostic Tests

Allergy Skin Test

Gold standard for allergen detection. A positive test result (red, raised bump) indicates sensitivity.

RAST (Blood Test)

Used when skin tests are unsuitable. It is generally less accurate, costlier, and provides slower results compared to skin tests.

How to Reduce Dust Mites in Your Home

• Wash beddings weekly in hot water (at least 55-60°C or 130-140°F) and dry thoroughly, preferably in the sun or a hot dryer.
• Use airtight, allergen-impermeable covers for pillows, mattresses, and duvets.
• Avoid upholstered furniture and carpets where possible. Prefer hard floors (wood, tile, vinyl) and leather or vinyl furniture.
• Ventilate your home well daily. Avoid damp areas and fix leaks promptly.
• Limit pet access to bedrooms, especially the asthmatic's bedroom, and wash pets often if applicable.
• Dust surfaces regularly with a damp or electrostatic cloth, not a dry one which stirs up dust. Wear a mask while cleaning.
• Keep soft toys away from the bed, or wash them frequently in hot water and dry thoroughly. Freezing them periodically can also kill mites.
• Vacuum thoroughly weekly, including mattresses, upholstered furniture, and carpets (if unavoidable). Use a vacuum with a HEPA filter if possible.
• Use air conditioners and dehumidifiers to maintain low indoor humidity (below 50%).
• Asthmatics should ideally avoid doing the dusting or vacuuming. If they must, wearing a mask is recommended. They should leave the room during cleaning and wait at least 20 minutes before re-entering.

Managing Your Asthma

Controlling asthma effectively involves more than just avoiding triggers. You should also:

• Understand your specific asthma condition.
• Identify and actively avoid your personal triggers.
• Use your prescribed controller and reliever medications correctly.
• Learn to recognize the signs and symptoms of worsening asthma control.
• Develop and follow an asthma action plan created with your doctor.
• Attend regular checkups with your healthcare provider.

Other Asthma Triggers Include:

• Pollen, mould spores
• Tobacco smoke (firsthand and secondhand)
• Pets (dander, saliva, urine)
• Cockroach droppings and body parts
• Exercise (Exercise-Induced Bronchoconstriction)
• Cold, dry air
• Air pollution (ozone, particulate matter)
• Perfumes, strong smells, chemical fumes
• Aspirin and some other medications (like beta-blockers, NSAIDs)
• Certain foods or food additives (e.g., milk, eggs, peanuts, sulfites) - though true food allergy triggering asthma is less common than often thought.
• Strong emotions (stress, laughter, crying, fear)
• Workplace chemicals or dust (e.g., wood dust, flour dust, di-isocyanates in paints/foams)