Green’s Dictionary of Slang

1. a casual sex encounter, because ‘You pick it up, blow, and throw it away’.

1996

A. Mudry World Enough and Time 186: Women are not usually into casual sex. I always describe it as ‘kleenex sex’: you use it, you throw it out.

2. among paedophiles, a description of those they exploit.

1988

L.R. Ashley ‘Sexual Sl.’ in Maledicta 157: The child victims [...] under your control) [...] are simply kleenex (‘pick it up, blow, throw it away’).

3. (N.Z. gay) an underage male prostitute.

2010

W. Ings ‘Trolling the Beat to Working the Soob’ in Int’l Jrnl Lexicog. 23:1 71: In New Zealand there have been many terms for a young male street worker. [...] A Kleenex was a young boy who was the target of adult men. The term came from a brand of paper tissue, with the tag line ‘Pick it up. Blow. Throw it away’.