The net is having a profound effect on medicine, as in all fields, not least because researchers in medical labs can share research with colleagues around the world.
By Sevan Lawson
BBC Click Online
There are also thousands of websites claiming to be able to diagnose and cure illnesses online, but there are concerns about how much the information provided can be trusted.
The net is becoming a 'second opinion'
Although a physical appointment with a GP might provide a quick diagnosis and prescription, many feel it is not long enough to get enough information about health problems.
The net is providing many with what they want, and this is creating a growing breed of so-called cyberchondriacs.
A survey by the Health on the Net Foundation found that about 50% of people used the net to get a second opinion.
Just over half of patients who discussed the results of net searches with their doctors found the consultation more constructive.
More harm than good?
However, self-diagnosis over the net can be a real minefield.
The information can cause confusion and unnecessary alarm. More worryingly, surfers could also be left out of pocket.
There are hundreds of unscrupulous sites which exist purely to make money.
"The problem with these self-diagnosis websites is that it's a misnomer," Dr Paul Cundy from the British Medical Association told BBC World's Click Online.
"The concept of diagnosis is that you engage in a consultation, and maybe investigations, with a professional, and after that you then agree upon a diagnosis."
The consultation is rather one-sided, and patients often do not know who they are talking to or what their motives are.
In many cases, it does not take long to find out.
Countless sites ask for an e-mail address, before guiding users through endless windows asking to pinpoint areas of discomfort, and tick boxes about general health.
After the questions, one expects to see the results, but instead, users are offered a health report at three different prices with a request for credit card details.
There are also many sites which ask for a one-off payment or subscription fee - often for three months - for making a diagnosis.
What surfers are likely to get for the money could be inaccurate, false or unreliable information, and sites often cover themselves by with an advice line like, "if you're worried you should go and see your doctor".
Although self-diagnosis has its limitations, carefully vetted and endorsed health sites do exist and can serve a good purpose.
Users can get health information on topics ranging from diseases and conditions to therapies and treatments.
The reputable sites have experts and consultants as advisers and can act as an important aid to patient care.
Doctors have realised the importance of being available to their patients outside normal surgery times.
Pills bought over the net are not regulated
As a result, e-consultations and e-doctors are changing the way traditional health care is provided.
Dr Julian Eden started his e-doctor's surgery four years ago, when he found people in remote diving locations e-mailed him for up-to-date advice.
"It's not so much a question of distance from your doctor, it's also time," he explained.
"If you can't see your GP for two weeks, you might as well be 3,000 miles away. So we found that what we can apply with diving medicine also worked very well for normal medical illnesses in the UK.
"As long as you get good information coming in about a medical problem, then quite often you can make an accurate assessment and diagnosis where appropriate for that condition."
Once trust has developed between a patient and an e-doctor, this type of service can be indispensable where access to a regular GP is difficult.
"It's also very useful for me because I travel a lot and it doesn't really matter where you are," said e-patient Jon Lane.
"If I've got a mobile phone or a laptop I can get in touch with him and I can get a prescription pretty much anywhere I am."
The Health on the Net Foundation have developed a code of conduct for approving sites, and they have a search tool to find sites which are safe to research.