Up to 5 per cent of the population is thought to have this sensitivity, which is recognised in Sweden as a disability. In Stockholm sufferers can have their homes adapted to remove or screen out sources of electromagnetic radiation. If this proves ineffective, they can even rent council-owned cottages in areas of low radiation.

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However, Dr Clark is not persuaded that electromagnetic fields are the cause of sensitivity. “While we accept that some people experience genuine symptoms, which can be distressing, what causes them is another matter. Most scientists are very sceptical because of the published laboratory investigations of electrosensitivity. People who are convinced that they can tell when they are in the presence of electromagnetic radiation cannot detect the fields in double-blind laboratory conditions.”

An important study by the University of Essex, due to be published next year in a peer-reviewed journal, may settle the matter. During the trial, 55 people who believe that they are hypersensitive and 120 non-sensitive controls were subjected to tests of concentration and memory while signals from second and third generation mobile phone masts were switched on and off. The trial was double blind: neither the researchers nor the subjects knew when the signals were firing.

Some believe that sensitivity symptoms are not the only threat posed by electromagnetic radiation. A Swedish study suggests that there is an increased risk of acoustic neuroma (an auditory nerve cancer) in people who have used mobile phones for more than ten years. Conversely, last week the results of the largest and longest-running study on mobile phones and the risk of cancer, published in the Journal of the National Cancer Institute, found that there was no link.

A literature review conducted by the International Commission for Non-Ionising Radiation Protection concluded: “Results of epidemiologic studies to date give no consistent or convincing evidence of a causal relation between exposure from radio frequency fields (RFs) and any adverse health effect. On the other hand, these studies have too many deficiencies to rule out an association. Despite the ubiquity of new technologies using radio frequency fields, little is known about population exposure from RF sources, and even less about the relative importance of different sources.”

And here lies the nub of the problem. Not enough research has been done over long enough periods on the effects of various levels of exposure on different populations to draw any firm conclusions about the dangers, if any, of wireless networks. As to whether the convenience is worth the risk – only you can decide.

‘I FELT DIZZY AND NAUSEOUS’

“Electrosensitivity” is a rather misleading term. I’m fine around electricity. But put me next to a BlackBerry or a wireless laptop accessing the internet and I feel dizzy, slightly nauseous and my flesh tingles as if it’s being scrambled. It sounds bonkers I know. But after years of denial I have had to come to terms with the fact that aspects of this fantastic new technology do not agree with me.

We installed wi-fi in our house two years ago. We loved it. The whole family could be online at the same time. I imagined myself working in the garden during the summer (although I never did), and I could work in bed. But from the moment wi-fi arrived I felt peculiar.

I mentioned casually to my husband that I could tell when he was sending an e-mail, but he dismissed that as laughable: I must be imagining it. So I put the idea out of my mind. But as the weeks and months passed I began to feel iller, overwhelmed at times by intense giddiness, headaches and a sense that I was moving through a dense fog. Sleep was fitful and I seemed to feel constantly at a low par.

Then we went away for the Easter break to stay with friends in the depths of remote countryside. I felt great as you tend to do when you’re on holiday. But the moment we walked back into our house I felt giddy and nauseous again and then I knew. I wasn’t neurotic. This was real.

I changed our router back to wired internet access. I had the computers reconfigured so that they no longer sent out signals searching for wi-fi and we binned the dect phones (digital cordless phones) just to make doubly sure. My husband began to notice the change in me within days and, finally, he believed me.

The trouble is that you can’t talk about this without people thinking that you’re mad. My symptoms are minor compared to others I have heard of. Sometimes I notice wi-fi in the wider world when it’s heavy — my local bookshop, the Apple Mac shop, airports and an expensive hotel we recently went to stay in. Other times I feel this scrambled fog only when I’m near a device using this technology — the hand-held machine in restaurants that you tap your pin number into and laptops surfing the web.

After months of monitoring, I’m happy knowing that it is wi-fi that makes me feel this odd and not some other unknown disease. I avoid it when I can. I don’t see much difference between someone smoking a cigarette or shouting into a mobile phone next to me in a public place. If anything I think I’d prefer the cigarette.

Poppy Rhodes

GET PROTECTED?

For anyone concerned about exposure to electromagnetic fields, the following companies claim that their devices offer protection:

EMFields: 01353 778814, www.emfields.org

Subtle Field Technologies: 01787 224377; www.subtlefieldtechnologies.com