A papule is a circumscribed, solid elevation of skin with no visible fluid, varying in size from a pinhead to 1 cm.[nb 1] They can be brown, purple, pink or red in color, and can cluster into a papularrash. The papules may open when scratched and become infected and crusty.
Papules may have different shapes and are sometimes associated with other features such as crusts or scales.
^With regard to the quote "...varying in size from a pinhead to 1cm," depending on which text is referenced, some authors state the cutoff between a papule and a plaque as 0.5cm, not 1cm, while others state an entirely different measurement. Therefore, for this article, the 1cm cutoff is used which is discussed in Andrews' Diseases of the Skin: Clinical Dermatology (see references), a work considered by some dermatologists as an authority on this subject matter. See Lack of Standardization for complete discussion.
^James, William; Berger, Timothy; Elston, Dirk (2005) Andrews' Diseases of the Skin: Clinical Dermatology (10th ed.). Saunders. Page 15. ISBN 0-7216-2921-0.