Measurement of the redox properties of household dust is used to detect the presence of allergen-associated materials. Measurement may be electrochemical, preferably amperometric. A disposable electrode assembly may be made by screen printing with conductive (e.g. carbon and Ag/AgCl) inks. An absorbent pad overlying the electrodes can be used to wipe a surface to collect a sample. It may contain electrolyte and buffer components, so that adding water carries sample in an electrolyte/buffer solution to the electrodes.