The products were categorized into four groups. 1. Tightly woven material of various pore sizes. 2. Woven material with added microscopic membrane 3. Non-woven polypropylene material 4. Cotton fabric treated with a nonspecific mite-killing chemical.
In a chambered experiment the doctors took clinically measured amounts of mite allergen (Der p1) and the smaller cat allergen (Fel d1) and pulled them through each product at a steady rate for 5 minutes. Particles that passed through were collected on a filter and measured for allergen content. This procedure was completed three times for each branded product tested. The results were compared to the same test on normal cotton fabric. Please note, in the results cat allergens are said to be smaller than mite allergens.
Results and recommendations. 1. Tightly woven - Evidence of cat allergen leakage in three of the five products tested, but no mite allergen was found. Good air permeability in all products. 2. Woven material with a microscopic membrane - Effective in preventing cat or mite allergen leakage. No air permeability in the three products tested. 3. Non-woven - Cat allergen leakage noted in one of two products, cat and mite allergen leakage found in the other. Good air permeability. 4. Cotton fabric with mite killing chemical - Evidence of both cat and mite allergen leakage in the single cotton products treated with nonspecific mite killing chemical. Air permeable. This study concluded that the best products tested were of a tightly woven washable fabric, air permeable and with a pore size small enough to prevent mite and cat allergen leakage. The study authors recommended buying a product with a pore size below 6 microns.
Please note; mite allergens have also been found to be 1 micron in size. Barrier protection that is not air permeable but proven effective in excluding cat or mite allergen may offer greater security. However, for people with atopic dermatitis, eczema or other related skin disease may need to take further precautions. See 'how to keep a mite-free bed' instructions on this site for help.
'Efficacy in allergen control and air permeability of different materials', Peroni et al, Allergy, 2004, Vol 59, Issue 9: p 969-972