The first home test which says it can reassure patients they are free of HIV has been launched in the UK.
HIV tests are usually carried out on blood taken by a nurse or doctor
The public can send in a saliva sample to a laboratory, and, if negative for HIV, receive results via e-mail.
Home tests were banned because counselling was not on hand, but the 'Dr Thom' kit offers phone support if it does not give the all-clear.
But Avert, a leading HIV/Aids charity, said patients worried they were infected should have an NHS test.
The Dr Thom test, which costs £25, looks for antibodies for HIV in the saliva, which suggests that the virus is present in the body.
When the test detects signs of an immune response to HIV in the saliva, the service offers a phone call from a 'health professional'.
Patients are also advised to seek a formal diagnosis from a genito-urinary clinic.
The Dr Thom service is being marketed at people who are concerned about HIV, but who do not want to visit a clinic to be tested.
The test is not as accurate as the normal blood test offered in clinics, and this will still be required in order to confirm the infection.
If the test is negative, results can be sent out by e-mail. If antibodies are detected, the person receives a call from Dr Thom recommending they have the further tests.
The saliva test is also unlikely to detect a recent HIV infection - only people infected more than 14 weeks previously will test positive, slightly longer than the interval needed for a reliable blood test.
The Health Protection Agency says that approximately a third of people in the UK who have HIV have no idea that they are infected.
A spokesman for DrThom said: "The test can tell if a person shows no signs of HIV, but is unable to make a firm diagnosis."
Annabel Kanabus, the director of Avert, said that the main market for the test was likely to be the 'worried well'.
She said: "I would still recommend that if people are genuinely worried they may have HIV, they should go to a local NHS genito-urinary clinic to be tested.
"The blood test is more reliable than a saliva test, and it is free of charge.
"In addition, counselling is available on the spot, unlike this service."