Over the last decade, bed bugs have re-emerged in the developed world. They can now be found even in 5-star hotels. They live in bedding and under mattresses and feed on blood. They hide during the day but emerge during the night to feed on their sleeping host. Their faeces appear as clusters of tiny spots and contain histamine, a chemical known to cause allergic reactions such as asthma, itchiness, sneezing and watery eyes. There are treatments available to get rid of bed bugs, but their poo can remain in mattresses, carpets and furniture upholstery long after the bugs are gone.