Saliva testing is already widely available in the US
A London NHS trust has become the first in the country to offer an HIV saliva test that provides definitive results on the spot in 20 minutes.
The test uses a toothbrush to pick up HIV antibody markers from the gum line.
Barts and the London NHS Trust hope more people will seek testing if the need to give blood and wait perhaps up to a week for results is eliminated.
The UK has the highest number of new HIV infections in Western Europe - more than 7,700 in 2007.
Gay men accounted for 41% of those new cases, with the bulk of heterosexual infections having occurred abroad.
But these figures do not take into account the estimated third of HIV-infected people who are unaware they have the virus.
Saliva tests are not new - and are indeed widely available in the US.
Home saliva tests are banned in the UK because counselling is not to hand, but Barts has become the first to offer the mouth swab on the NHS and provide almost immediate results.
About 200 people in the trust's clinics have undergone the test since March, and it is hoped about 250 patients per month will take the test in the future.
It is available in non-healthcare settings such as outreach centres, and the trust's sexual health workers even hope to start taking it into clubs.
"We have got to a point in this country where HIV is a long-term treatable condition akin to diabetes. That message hasn't yet filtered through and stigma does remain around HIV, even if it is waning," says Merle Symonds, head of sexual health advising at the trust.
"What's crucial is that we pick it up early, before you get ill. We hope a very straightforward saliva test like this will encourage more people to come in and find out if they are affected. The sooner you know, the better."
Lisa Power of the HIV charity Terrence Higgins Trust, which also offers a saliva test, said one of the key problems was that many people in the UK carrying the virus did not know they were infected.
"This is a danger to their own health, but also means they can pass it on to others without knowing. Anything we can do to increase the take-up of testing is welcome, and we think what Barts is doing is fantastic.
"People need to know that if you are diagnosed with HIV in your 30s and start an NHS programme of treatment you can live into your 70s. Of course there may be some health problems, but this is no longer a death sentence - far from it."