A Pandora's box has been opened and there is no closing the lid now. Medical lore has been let loose. It is no longer the secret preserve of physicians. It is out there for anybody and everybody to possess.
The internet has proved itself the ultimate democratising tool, sweeping away the old medical culture which said that although we own our bodies we are not competent to understand how they go wrong and what options there are for fixing them. Now we have access to the same information, the same published studies and the same clinical trials data that doctors have.
If the internet has filled any need, it is the need to know more about health and medicine. Health websites are proliferating faster than bacteria. These are heady times, but there are potential problems too. There is so much information that it is hard to know where to start and how to find your way around.
And alongside the highly respectable sites are the well-meaning but just plain wrong - such as some of the proponents of vitamins as a cure for cancer - and the really dodgy, who want to flog pills and potions, from herbal remedies to Viagra.
The government has gleefully embraced the cultural shift that the internet represents and hopes to take it further, for a variety of reasons, some of which are to do with encouraging people not to visit doctors if they can look after themselves at home.
Its health website, NHS Direct Online, was launched in early December by Tony Blair under a hot-air balloon adorned with Christmas decorations in a shopping centre in Bootle. Health on the net is for everyone, was the unmistakable message, not just the affluent middle classes with their dual email addresses - at home and at work. NHS Direct Online some time this year will turn up in free kiosks in hospital waiting rooms and supermarkets.
So far, it is scoring more hits than expected. Bob Gann, the man in charge, says they are averaging 100,000 a day. What took them by surprise is that the main interest is not in people working out what disease they might have from checklists of symptoms; those logging in have already been diagnosed by a doctor, and they want to know more about their medical problem.
This quest to know more is what the internet is all about. The National Electronic Health Library (NEHL) - the NHS database of approved trials and studies - will allow patients to find out even more when it finally gets up and running. They can do it now through Medline, the huge US government database, but the NEHL will be British and easily accessible through NHS Direct Online. "The idea of separate information for patients and doctors will become quite redundant really," says Gann.
But there is a big debate going on over the way information is presented by the NEHL. Who is it for? For doctors, certainly, but also for the community midwife who comes across a medical disorder she has never met before; and the mother who has been told her child has a chromosomal defect.
If NEHL is to offer an archive of approved medical texts - kitemarked is the word that has been mentioned - it will become inaccessible to the ordinary man or woman. But others argue that anything more simplistic, produced by lesser mortals than five-star academics, cannot be guaranteed accurate. Any sort of checking system would be enormously time-consuming, expensive and difficult.
It is not just worthy sites such as the NEHL that are troubled by this argument. There is a tension for all website designers between the original free and easy, anti-authoritarian atmosphere of the internet, where all information is the property of everybody, anybody can post their views and censorship is unthinkable; and the desire of many health interest groups to protect the public from sharks and the ignorant.
Look at the chat rooms on health sites for instance. Much of what is posted is banal banter and gossip, just as it is in every other chat room. But there are also people with quite desperate-sounding problems, and there are salesmen pushing "breakthrough" treatments.
Gann says he would like to look into the possibility of running a chat room on his site, but "the problem is that they are unmoderated". It would surely be unthinkable to find bad information on a government website. So the alternative is some form of screening. Patient groups think the same way. But the implicit censorship sticks in the craw of the internet purists. And how much effort are you going to put into checking people's facts before you let them put forward their views?
On the credit side, the internet has been fantastic for those who have been isolated or cut off from information they need, such as families whose children suffer from very rare diseases. In the UK, an organisation called Contact a Family has been up and running for 20 years. Its aim is to bring those isolated families and the doctors and nurses who work with them together to pool their information and support each other. The internet has transformed their lives and their hopes. The charity is now able to link people with a common interest and a real need for information across the world.
"A mum in Norway rang in November," says Harry Marsh, who heads the charity. She had a child with a chromosomal condition called Smiths-Magenis. "There are only five families in the whole of Norway with that condition. I put them in touch with the English group, which is quite sizeable." He says the impact of the internet for Contact a Family has been colossal. "For most of last year, we were getting 3,500 to 4,000 hits a week on the site. In a generous year we used to get 10,000 contacts on paper. We're getting 20 times the interest we got before."
However, he worries about the quality of information people can be given through the net. "Families, particularly where they haven't been given a clear diagnosis, are desperate for information and they are quite vulnerable. Some would say they were quite vulnerable before, when they would leaf through medical encyclopedias. But if you can sit down and access 100 horrible things in an hour, it is a different league." Entries to his organisation's site have to be approved by qualified medical personnel, he says.
There is almost certainly a middle way between the need some have for 100% non-alarmist, accurate information, and the fun free-for-all, disrespectful web others enjoy. There is more and more signposting around. NHS Direct does it, government information sites in Australia, the US and elsewhere do it, and some very respectable patient groups do it too. They all give lists of dependable sites for patients who want serious information about diseases and treatments.
Those who have a more casual, curious or voyeuristic interest in health have plenty of other options. There are hosts of sites which answer your questions about weight loss, healthy lifestyles or sexual health, and offer questionnaires to check your fitness.
The bulletin board for one of them, Onhealth, www.onhealth.com, accessed through the search engine AltaVista, gives a clue to people's priorities. Weight gain tops the list of questions and comments posted - 1,817 at the last count - with sexuality on 787, healthy eating on 495 and stress and anxiety on 403. In the subset of diseases and conditions, 545 were concerned about aches and pains, 323 asked about gastrointestinal problems, and 322 about back pain. A further 656 wanted to discuss pregnancy, and 469 were interested in alternative health.
Serious medical problem or lifestyle anxiety - there is room for all in the end. They key is to follow reliable signposts, or go browsing with a healthy scepticism.
