The myth

The chief ingredient of household dust is human skin; 70, 80 or 99 per cent, in various versions

The "truth"

There seems to be no basis at all for this Well Known Fact – except wishful guesstimating on the part of those advertising copywriters whose job it is to sell us anti-dust devices. There’s no evidence to suggest that dust is mostly made up of any one ingredient; rather, it is a delightful salmagundi or potpourri of everything that is likely to be drifting around your house – cat dander, face powder, cigar ash – or that might be blown in every time you open the door, including soil, pollen, insect excreta, and general industrial pollution.