"Fragrances can include tens to hundreds of different chemicals, some of which are toxic, and many of which are known allergens, like limonene and linalool. All fragrance chemicals are usually kept secret from consumers. Dryer sheets can contain volatile organic compounds like acetaldehyde and butane, which can cause respiratory irritation. Quats, a fabric softener chemical, is often part of a family of chemicals called quaternary ammonium compounds, many of which are linked to asthma. Acetone, used in dryer sheets, can cause nervous system effects like headaches or dizziness.
Not surprisingly, when asked, survey respondents frequently report adverse health effects from exposure to dryer vents. One study found nearly 11 percent of the respondents reported irritation from exposure to emissions from dryer vents vented outside. Nearly 40 percent of respondents who indicated that they were “chemically sensitive” reported irritation from dryer vent emissions."