Silk pillowcases can reduce your chemical exposure.
Silk is a natural protein fiber made from silk cocoons. Silkworm spins a thread out of material from its own body, and winds around itself, forming a cocoon. If the cocoon are not disturbed, in the ordinary life process of the silkworm a moth would come out. The moth would lay eggs and die, and the process would start over again. Silkworms live in very clean room and eat mulberry leaves which is 100% organic food for them. Thus, the living environment of silkworm, and the production process of silk is 100% clean and chemical-free. No pesticides at all.
Compared with other textiles like cotton surrounded by pesticides to ensure the living of cotton plant, and polyester which is made from oil, silk is indeed the best natural, chemical-free fabric we can find nowadays.