This news article mentions a complaint called 'PVC bottom'. Knickerless must be mainstream or such an illness would not have been identified and named!
here is an abstract from the article (link below):-
"The conference, sponsored by Liverpool University and the regional office of the NHS executive, was organised after hospital staff became alarmed at the number of injured revellers appearing in accident and emergency departments. Among the problems were 'PVC bottom' (the chafing which results from knickerless friction) and 'clubber's nipple' (a painful condition arising from jumping up and down for long periods clad in a string vest). More serious are the results of poor water supplies, indiscriminate sex, and over-enthusiastic bouncers"