Which synthetic fabrics are allergy-friendly?

Polyester is a good bet. This synthetic material is hypoallergenic and quite durable. Most polyester rugs these days are made from recycled materials, making them more environmentally friendly. Olefin (polypropylene) is stain and moisture resistant, which means there won't be a buildup of mold, that can also activate allergies. Nylon is a strong material with a high resilience. It's very easy to clean, and won't trap dust mites and bacteria.