They claim to detect allergies, genetic disorders and even cancer. But tests and potions sold via the internet could cost you dear, says Roger Dobson

The therapeutic steering wheel cover seemed to have everything. Its raised bumps would not only help identify any health problems that needed treating while you were driving, it would also cure them by massaging key pressure points as the wheel moved.

The therapeutic steering wheel cover seemed to have everything. Its raised bumps would not only help identify any health problems that needed treating while you were driving, it would also cure them by massaging key pressure points as the wheel moved.

Should the wheel not work for you, what about trying the Chinese health slippers, or the body contour test, or the "never been shown to be wrong" cancer test?

Although gizmos like these are claimed to be able to detect or cure a wide range of different diseases and unhealthy conditions, they do have one thing in common. Each has made it onto Dr Stephen Barrett's list of dubious devices.

The psychiatrist, now retired, has spent more than 30 years on a crusade against dodgy medical tests and cures. Hundreds of them are listed on his websites, which are consulted by more than four million potential customers of these "cures".

Since the arrival of the internet, Dr Barrett has had his work cut out for him, with an explosion in health tests and medical gizmos. Many are expensive and most make extravagant claims - but few, if any, have been subjected to clinical trials. In addition, as many are sold internationally, it becomes that much more difficult for disgruntled buyers to track down the companies behind them when things go wrong.

The problem for consumers is that there is little independent advice available. There are so many tests on the market that family doctors are unlikely to have heard of many of the genuine ones, let alone the more dubious.

It is estimated that there are now more than 500 different types of test available via the internet. There are blood tests, urine screens, skin tests, and health profiles for almost any condition. There is a clot test, which purports to measure the length of time a spot of our blood takes to clot as an indicator of health. There are lymph gland sensitivity tests, nutritional blood profiles, oxygen stress tests, herbal hair analysis and saliva tests for ageing and the menopause. More worrying still, there are "cancer detectors" and even a "cancer zapper". There is muscle testing for allergies, tongue diagnosis, food allergy screening and a comprehensive digestive stool analysis.

Although some of these are unlikely to hurt anything but the buyer's bank balance, many can be damaging, especially to the vulnerable and the sick.

To the healthy, these tests and curative devices are dubious - even ridiculous - but those diagnosed with a serious illness, and patients in chronic pain or with a degenerative disease, are naturally much more ready to believe in their claims.

"Despite the advanced state of medical science, many people with health problems turn to dubious methods. Faced with the prospect of chronic suffering, deformity or death, many individuals are tempted to try anything that offers relief or hope. The terminally ill, the elderly and various cultural minorities are especially vulnerable to health frauds and quackery. Many intelligent and well-educated individuals resort to worthless methods in the belief that anything is better than nothing,'' says Dr Barrett, who is also vice president of the US National Council Against Health Fraud.

Two areas where there is most concern are cancer tests and treatments, and gene testing. Some of the cancer devices are seen as particularly insidious because patients faced with few mainstream options will try almost anything. Concerns about the risks of inherited disease have also increased demand for the growing number of gene tests on offer over the internet. Critics of these tests believe they trade on people's fears of becoming ill.

Dr Helen Wallace, Deputy Director of GeneWatch UK, wants better regulation of genetic tests: "There is currently no regulation for genetic tests as to whether the claims made are true in terms of your risk of future illness, and the kind of action you should take. We are seeing tests on the internet which make claims about your genetic risk for common diseases which most scientists would say are not supported by current science. That means that at best people are being ripped off, but at worst there could be serious implications for people's health.''

Among the purveyors of online health products, Dr Barrett is not a popular man. He has been described as arrogant, closed-minded, a bully, a thug and a Nazi. Now, he is working on providing another service to consumers: the Internet Health Pilot, which will be using the services of about 700 experts on health-related subjects, is aimed at creating a list of up to 500 of the best online health sites for consumers.

Meanwhile, he has the following advice for those tempted to buy over the internet:

* Remember that quackery seldom looks particularly outlandish.

* Ignore any practitioner who says that most diseases are caused by faulty nutrition or can be remedied by taking food supplements.

* Be wary of anecdotes and testimonials.

* Be wary of pseudo-medical jargon, especially the terms "detoxification" and "nerve energy".

* Don't fall for paranoid claims, such as that the medical profession, drug companies and the Government have a secret agenda.

* Forget about "secret" cures.

* Be sceptical of any product that is claimed to be effective against a wide range of unrelated diseases - particularly diseases that are serious.

* Ignore appeals to your vanity.

* Don't ever let desperation cloud your judgement.