P M Fleiss, F M Hodges, R S Van Howe, "Immunological functions of the human prepuce" SEXUALLY TRANSMITTED INFECTIONS (London), Vol 74, Np 5, pp 364-367, 1998. http://www.cirp.org/library/disease/STD/fleiss3/
>The inner prepuce contains apocrine glands, which secrete cathepsin B, >lysozyme, chymotrypsin, neutrophil elastase, cytokine (a non-antibody protein >that generates an immune response on contact with specific antigens), and >pheromones such as androsterone. Lysozyme, which is also found in tears, > human milk, and other body fluids destroys bacterial cell walls.
>The natural composition of preputial bacterial flora is age dependent and similar >to that of the eyes, mouth, skin, and female genitals. Washing the preputial sac >was once thought to aid hygiene. Washing a stallion's preputial sack with soap, >however, encourages the growth of pathogenic organisms Washing the human >prepuce with soap is a common cause of balanoposthitis.