Allergen Barrier Filtration Testing is more important than ever in Textile

The thread count myth: why it tells you nothing about allergen performance

The textile industry has long used thread count as a shorthand for quality — but its relevance as a performance indicator has been eroding for years. In a 2011 article in Home Textile Today, Editor-in-Chief Jennifer Marks highlighted the growing confusion around thread count inflation and predicted it would drop into obscurity on consumer packaging. For those making allergen barrier claims, the problem is more acute: the assumption that higher thread count equals smaller pores, and smaller pores equal better allergen blocking, is scientifically incorrect on both counts.

Pore size measurement: why bubble point is not sufficient

Pore size is most commonly assessed using the bubble point method — quick and relatively inexpensive, but limited by its inability to account for unopened pores and the natural variation in pore size across a fabric. Scanning or projection microscopy provides a more accurate picture, with the additional benefit of producing images that directly illustrate warp and weft structure. These images consistently demonstrate how high thread count claims can be made without any corresponding reduction in functional pore size.

More fundamentally, pore size only loosely correlates with allergen filtration efficacy. Two additional factors significantly influence whether an allergen particle passes through a textile:

• Van der Waals forces — electrostatic interactions between allergen particles and fabric fibres that cause allergens to adhere to or pass through textile surfaces independently of pore geometry.
• Allergen conformation — the three-dimensional shape and aerodynamic properties of allergen particles, which determine how they interact with textile structure under airflow conditions.

What allergen barrier claims must actually cover

When a textile product claims to be an allergen barrier, it is making a specific scientific assertion — that it blocks allergen particles of defined sizes under real-world conditions. The three most clinically significant allergen categories for bedding are:

Glass bead filtration methodologies — traditionally used in military filter evaluation — have been applied to textile testing but have not been shown to be accurate predictors of allergen behaviour in fabrics. Glass beads do not replicate the aerodynamic or electrostatic properties of biological allergen particles, and results from this method should not form the basis of consumer-facing allergen barrier claims.

Direct allergen filtration: the correct approach to allergen barrier testing

The first description of direct allergen filtration in textiles was published by Vaughan et al. (1999) in the Journal of Allergy and Clinical Immunology. The paper — “Evaluation of materials used for bedding encasements: Effect of pore size in blocking cat and dust mite allergen” — used a modified Fussnecker dust trap to establish a methodology that remains the foundation of rigorous allergen barrier evaluation today.

How the test works

A dust sample containing a precisely measured quantity of allergen is drawn across the test fabric under controlled airflow. A downstream filter captures any allergen particles that pass through. These are extracted and quantified using ELISA kits specific to each allergen type — the same immunological assay used in clinical diagnostic testing.

The method provides two measurements no proxy approach can deliver: direct airflow measurement (critical for comfort and breathability claims) and a precise, reproducible allergen filtration efficiency figure expressed as a percentage. This is the number that can be cited in marketing materials, technical documentation, and regulatory submissions — and that will hold up when challenged.

Simulated use testing: evaluating performance over time

Static filtration testing establishes baseline allergen barrier performance under controlled conditions. Simulated Use Testing extends this by replicating how a product is actually used — repeated laundering, compression, and mechanical stress over a product’s commercial lifespan.

Fabrics that perform well under initial testing can show significant degradation in allergen filtration efficiency after washing cycles and sustained use. For manufacturers making durability claims, or retailers specifying wash performance on packaging, Simulated Use Testing provides the only robust evidence base. Together with direct allergen filtration testing, it forms a complete evaluation framework covering both initial and sustained allergen barrier performance.

Airmid Healthgroup and the AAFA certification programme

Allergen barrier testing and research for the Asthma & Allergy Friendly® Certification Program is conducted by Airmid Healthgroup Ltd (AHG). This certification programme is operated by Allergy Standards Ltd (ASL) — an international standards and certification body whose independent textile standards are developed in consultation with industry, retailers, and healthcare professionals, and are the only standards accepted by the Asthma and Allergy Foundation of America (AAFA).

AHG’s textile research spans all disciplines relevant to indoor particulate contaminants: virology, microbiology, mycology, allergen detection, dust mite evaluation, and bed bug research. This breadth of expertise underpins our position as the testing partner of choice for manufacturers and retailers seeking credible, independently verified allergen barrier claims.

What this means for retailers and manufacturers

The confusion between thread count, pore size, and allergen filtration has persisted in the market for decades — not always through deliberate misrepresentation, but through reliance on insufficient test methods and a lack of clear industry standards. That environment is changing. Regulatory scrutiny of health-adjacent product claims is increasing, and the documentation required to defend an allergen barrier claim in a legal or regulatory context is more demanding than it has ever been.

Retailers should require direct allergen filtration test data — not pore size reports — as the minimum standard for any allergen barrier claim. Manufacturers should ensure their test methodology produces allergen-specific, quantified filtration efficiency data that an independent body can verify. And consumers looking for genuine allergy protection should look for third-party certification backed by this standard of testing.

A claim is only as strong as the science behind it. In allergen barrier testing, that science has a clear, established standard — and anything short of it is a risk.