So here is a pronouncement yesterday, from no less than the Scottish Tartan Authority that we kilties who prefer to wear not a lot under our kilt, are unhygienic and not too clean individuals!
This has made headlines in several of the Scottish newspapers today although the Scottish Kiltmakers Authority have argued against this pronouncement

Also on the side of the bare bums is former Formula 1 ace, Scotland's own, David Coulthard who says he is always commando and it is totally hygienic and allows the freedom of movement that the kilt gives

I suppose you may have to side with the STA who say that for kilt hiring shops, the state that they get the kilts back in would turn your stomach and cannot possibly be cleaned.
From my own point of view I tend to agree that perhaps some sort of barrier between body and garment is necessary when some of these kilties hiring ouitfits for one - off weddings etc really get well over the eight and have no experience about personal hygeine when wearing the kilt, perhaps a leaflet in toilet training should be given out with every hired kilt?