The fabric itself may also cause problems for those who are more sensitive. Try sticking with natural fabrics like cotton (organic when possible), silk, wool, and linen. Leather is 1 exception which releases formaldehyde due to the tanning process. Most synthetic fabrics such as polyester and rayon will also contain formaldehyde or some other chemical known to cause cancer. In addition, any clothing advertised as flame resistant or wrinkle-free are subjected to dangerous chemicals during the manufacturing process that can affect you - even after many washes.