Accounts of white fabrics and garments turning yellow during storage in polyethylene bags or wrappings have increased considerably in the past few years. Observations on the phenomenon are cited from world literature. A mechanism is given for the reaction of nitrogen dioxide from polluted air with butylated hydroxytoluene (BHT) from the polyethylene bags to give 3, 5-tert-butyl-p-quinone methide, the sought after yellowing species. The chemistry of this quinone methide and its relationship to various published observations is discussed. A suggested mode of acid finishing, as well as other practical approaches, are offered as means of avoiding problems with yellowing.