Rogue Internet sites are accumulating on the Web from all over the world, offering magic cures, warning of dire new diseases or giving bad advice even for simple ailments.
In other cases, patients, some with serious diseases, are given the impression they have stumbled across a miracle cure on the Internet.
David Pearce, a Leeds GP, said: "The main worry is that anybody can put information on the Internet about diseases. The false hope this can bring to patients, particularly those who are suffering from chronic illnesses and are very vulnerable, is terrible.
"There are even discussion groups where doctors will make diagnoses of people who type in their symptoms via the Internet. It's a nightmare."
On a recent British Medical Journal search of 41 Web pages to discover the best way to treat a child with fever, only four gave the correct diagnosis. The problem is proving particularly bad for doctors treating patients with serious illnesses.
When a person is first diagnosed, family and friends often search the Internet for information about the disease, leading them to large amounts of false advice. Peter Chambers, of the charity CancerBACUP, said: "The Internet provides an example of how a little knowledge is a dangerous thing."
He said some cancer patients acting on Web information took hydrazine sulphate, which is derived from rocket fuel and is ineffective against cancer, and stopped taking their anti-nausea and pain-relieving drugs when they reacted with the hydrazine. BACUP responded by creating its own Web site to provide accurate information.
Doctors tell patients interested in the Internet to use it wisely by accessing credible organisations and help-groups. Iona Heath, who has a surgery north London, said: "There is an awful lot of garbage out there ... but it can be helpful too. The Web can sometimes be very good for people with rare diagnosis when they can learn more than I can tell them."
John Chisholm, chairman of the BMA's GPs Council, said: "People have to use a bit of discretion when using the Internet but doctors have to recognise more and more people are going to be using it. Often they can become experts and get a lot of useful information."
Some GPs are worried they do not have the time to cope with the challenges of the Web. Grant Kelly, chairman of the BMA's General Practice Computing Group, said: "You get people coming into the surgery and saying `I want to try this drug or that treatment'. It's not a problem, as we can talk it over and usually explain why it is not appropriate, but it is all taking a long time and that's one thing GPs don't have."Reuse content