18th January 1998

Who's been sleeping in my bed?

Sweating in terror you are locked into a hideous dream of carnivorous aliens swarming over your body. The alarm jerks you awake. "It was only a nightmare," you think but in fact the real nightmare is only just beginning.

You roll out of bed, leaving your partner to luxuriate for a little while longer on her warm pillow.... where a small civilisation thrives. These are Dermatophagoides pteronyssinus - the flesh-eating pillow mites. Under the microscope they are hulking armoured beasts, with eight legs and massive rhino-like necks, which makes them superbly equipped for inside our pillows.

Their feet have flared pads like a creature from Star Wars, to prevent them sinking into the soft filling and since it is hard to see in the dim light, they signal romantic availability not by crude bellowing calls, but by the polite release of a floating vapour.

The insect swivels its huge neck to get a directional fix, and then, as gracefully and balletically as an armoured monster can, trundles hopefully and forward for the trysts that await, to produce yet more of these generations that live beneath us, microscopically nibbling our loose skin flakes.

Their population can be as low as 10,000 in ultra-hygienic home, but if this is the house where busy professionals only change the pillowcases, but neglect to rinse, soak, boil or simply wash the pillow itself, then the inhabitants can be discreetly fruitful and multiply for weeks, months or years.

In homes like this, each pillow might be home to 400,000 or more creatures. And with the half-pint of water vapour we exhale over them every night, they are safely incubated.

In the kitchen, dad opens a bottle of freshly-squeezed orange juice. Some of what's there actually comes from squeezed oranges, but that is pretty expensive stuff, so a lot of it is simply recycled pulp wash, a substance made by spray-blasting otherwise unusable rinds. Since pulp wash on its own tastes as terrible as you'd expect, sugar is added, then some of the active chemical from nail vanish remover, to give the pulp wash a palatable tang, and then varnish solvent, to keep that tang from getting too strong.

To stop the floating mess from breaking apart entirely, a dose of the embalming fluid formaldehyde - or a chemical near-cousin - goes in: the chemical is ideal at forming tight linking groups between proteins be it dissolved bits of cadavers or scattered flecks of pulpwash.

The first glasses are drunk contentedly, but the teenage daughter reacts furiously when more is offered her. Don't they realise that she just so happens to be on a diet? The mother tries to ignore the outburst, but several hundred nanograms of the peptide hormone ACTH are likely to be cascading down from her brain, in a reverberating response to her daughter's flare-up. This can upset her immune system for hours, making her more susceptible to cold viruses or other microbial assaults.

The baby, meanwhile, is sitting on the carpet and investigating his sister's leather jacket, which is coated with thousands of continence molecules, residue from the cigarettes she smoked the evening before. The molecules bounce off the leather into the air and float into the sniffing baby's lungs. Some of the molecules will pass into his bloodstream and end up, months hence, stored in his growing hair.

Blissfully unaware of this microscopic jungle, the family gathers itself for a trip to the shops. Outside the shopping centre now - the daughter lagging ostentatiously behind where solar photons which were speeding through space at the orbit of Venus just two and a half minutes ago crash on to the family. Everyone's mood unexpectedly goes up, for the crash-impacting phoons stimulate their endorphin levels to rise.

The parents pause at a food shop, eager to drink a liquid mash that plants evolved to fatally over-accelerate the neurotransmitters in ancient bulge-eyed insects. It is coffee, of course. When a non-dairy creamer is stirred in, it becomes attractively white as it is poured out. This is guaranteed by manufacturers mixing in titanium dioxide. It is the same whitener that sloshes around in buckets of white latex paint which is something to think about while sipping coffee outside a DIY store.

Back home, the tail-thumping dog is desperate to greet the returning family. If there is a big slobbery kiss and who can resist? - then several squiring Entamoeba gingivalis predators that live in the mouth of 50 per cent of domestic dogs will be tranferred over. These can survive for days or weeks in your mouth, squirming around our gums for their live bacterial prey.

The day is over, so it is up to bed. While dad turns the thermostat nice and high - ideal for boosting the pillow-mite population - mum helps her son fluff up his pillow. Each whacking compression shoots geysers of dust mite body parts into the room and they float down over the boy all night in allergy-inducing haze.

There is more to do, but the parents are tired. They climb the stairs to sleep, and to dream.

Excerpts from the Secret Family, by David Bodanis published by Simon & Schuster.

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