diameter ~14%: length <2 %
||Human Homo sapiens
||Robbins, Clarence R. Morphological and macromolecular structure, pp.1-62, chapter 1 in the book Chemical and physical behavior of human hair / Clarence R. Robbins.-2nd ed (2002) p.28 top paragraph
|| Paul B. Stam, Robert F. Kratz, Howard J. White, JR. The Swelling of Human Hair in Water and Water Vapor. Textile Res. J. 22, 448 (1952) link
||Primary source abstract: "Data are presented on the swelling of free and strained hair fibers in water and water vapor."
||P.28 top paragraph: "For example, from 0% to 100% relative humidity, hair increases
nearly 14% in diameter, but less than 2% in length [primary source]."