Biting insects in the office: what they are and what to do

When staff start reporting bites at work, worry spreads quickly. It is a problem worth taking seriously, but also one worth investigating calmly, because the cause is not always what people assume. Here are the usual culprits in offices, how they get in, and what to do.

01Fleas

Fleas usually arrive on clothing or bags from a home with a pet, or are already in a building that has stood empty after a previous tenant had animals. Flea eggs and larvae can lie dormant in carpet for months, and the vibration of people walking around triggers them to hatch. Bites tend to be around the ankles and lower legs, often concentrated in one area of the floor.

02Bed bugs

Bed bugs do not live on people, but they travel in bags, coats and second-hand furniture, and they can hide in upholstered chairs, sofas in breakout areas and the seams of soft furnishings. In an office they are more likely to be an occasional hitchhiker than an established colony, because there is no one there at night to feed on. Where they do establish, it is usually where people sit still for long periods, or where staff sleep on site.

03Bird mites

Birds nesting in eaves, behind signage or on ledges near windows and air intakes carry mites. When the young birds leave the nest, the mites lose their host and can wander indoors looking for another. They bite people but cannot survive on them, so the problem stops once the nest is dealt with, which should be after the nest is no longer in use, as active nests of wild birds are protected by law.

04Flying insects

Mosquitoes and biting midges can come in through open windows, particularly near water or in warm, still weather. The tiny flies often seen around office plants are usually fungus gnats, which breed in damp compost and are a nuisance but do not bite. Letting compost dry out between waterings deals with them.

05When it is not insects at all

Some outbreaks of "bites" in offices turn out to have no insect behind them. Dry air from heating and air conditioning, static, fibres from new carpets, insulation or paper, and reactions to cleaning products can all cause itching and red marks. That is why identification comes first. Treating an office for an insect that is not there costs money and solves nothing.

06What to do

• Record it. Note who is affected, where they sit, when the bites appear and what they look like.
• Catch a specimen if you can. A sticky trap near the affected desks, or clear tape pressed onto a suspect insect, gives something to identify.
• Keep it calm and discreet. If one person may have brought fleas or bed bugs in from home, handle it sensitively.
• Clean thoroughly. Vacuum carpets and upholstered chairs well, and empty the vacuum outside.
• Check the outside. Look for nests near windows, vents and air intakes.
• Keep food in sealed containers and clear desks of food at the end of the day.