Allergen barrier filtration testing is more important than ever in textile testing

By Máire Fox MSc

In a March 2011 article of Home Textile Today, Editor in Chief Jennifer Marks highlighted the confusion over ‘thread count inflation’ and its lack of meaning. Jennifer expects to see thread count identification drop into obscurity on packaging.

The issue over thread count has a further relevance for people wishing to make decisions with regards to pore size and allergen barrier efficacy. The tendency for many retailers to associate pore size with thread count and hence the bedding textile’s ability to block allergens is incorrect.

Pore size is often measured using bubble point as it is quick and fairly easy to do, however due to unopened pores and pore size variation it is probably better to do scanning or projection microscopy which also has the added benefit image generation. These images will also illustrate the warp and weft of the fabric demonstrating how the high threads count can be claimed but with no added benefit in pore size.

Pore size only loosely correlates with allergen filtration efficacy and there are a number of factors that contribute to this including van der Waals forces and allergen conformation. It is important to note that when a textile is claiming that it is an allergen barrier, it is claiming to block allergen particles such as Fel d 1 particles which are less than 10 µm in diameter and the mite faecal pellets, Der p 1 which ranges between 10 µm and 40 µm (however the dust mite itself has a size of 250 µm to 300 µm).

Therefore a direct way needs to be developed to measure filtration capability in order for retailers to make accurate claims. Glass bead filtration methodologies traditionally used in the military evaluation of filters have some benefits but again have not been shown to be accurate predictors of allergen behaviour in textiles.

The first description of direct allergen filtration used a modified fussnecker dust trap published in Journal of Allergy and Clinical Immunology, Vaughan et al (1999). This paper, Evaluation of materials used for bedding encasements: Effect of pore size in blocking cat and dust mite allergen, discusses the relationship between encasements that block allergen and also allow the passage of air through the material. This technique has the benefit of direct measure of airflow which is a key issue for comfort physiology and patient compliance. Dust samples containing a known amount of allergen are pulled across the fabric and a filter located downstream collects any allergen that passes through. The amount recovered on the filter is extracted and measured using an ELISA kit specific for different types of allergens. The data from this allows manufacturers and retailers to directly claim allergen blocking ability for fabrics against a number of allergens. Another method that also provides information regarding allergen barrier efficacy is the Simulated Use Test and this will be described and discussed in further articles.

Fabric analysis data of allergen filtration using the modified dust trap methodology (Allergen Barrier Testing with Airflow) is a key evaluation technique for Allergy Standards Limited (ASL) an international standards and certification body helping consumers and retailers identify bedding for people concerned about allergies, asthma and indoor air quality. ASL’s independent certification standards for textiles have been written in consultation with industry, retailers and health care professionals and are the only standards that are accepted by the Asthma and Allergy Foundation of America.

The Allergen Barrier Services such as testing and research for the Asthma and Allergy Foundation of America certification program is conducted by the life sciences company airmid healthgroup ltd (AHG). The AHG textile research spans all disciplines relevant to indoor particulate contaminants, ranging from virology, microbiology, mycology, allergen and also including dust mite and bed bug research. The AHG laboratory offers a complete range of advanced Allergen Testing Services specialising in Allergen Barrier Services, Dust Mite related Testing, Claim verification services and Allergen detection.

In summary, due to the continuing confusion of textile labelling where pore size and thread count is concerned, the Allergen Barrier Testing with Airflow evaluation of fabrics and textiles plays a vital role in correct claim verification where allergen is concerned. Reputable retailers should ensure that all allergen claims have been conducted in a meaningful way to avoid falling foul of labelling guidelines. Concerned consumers should also seek that all labelling where allergies are concerned have been validated by a third party independent testing authority.


Máire Fox
Máire Fox MSc is Head of Allergen Testing Laboratory. Máire graduated from NUIM with a BSc in Biology followed by laboratory analyst positions in the Biotechnology Unit in NUIM and the Vitamin Research Laboratory in TCD. Máire completed a research MSc in Prion Disease while working as a Laboratory Analyst in the Prion Research Laboratory in UCD. She subsequently worked in the Department of Agriculture investigating the molecular characteristics of BSE strains in Ireland. Contact details:

airmid healthgroup
At airmid healthgroup our mission is to prevent ill health caused by exposure to indoor air pollutants and dust mites. airmid healthgroup lists as its customers the Asthma and Allergy Foundation of America and Asthma UK.

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