IT became the background of their marriage, but eventually Joy Milne stopped talking about it.

But now the woman who found she could smell her husband's Parkinson's disease is telling everyone about her gift as she helps scientists edge ever closer to finally creating a test for the disease.

Mrs Milne, from Perth, has been described as a "wonder" by researchers and says jokingly she is “somewhere between a dog and a human” because her one-of-a-kind nose can detect the odour of the disease.

She first detected the scent coming from her husband late Les years before he was officially diagnosed and later told researchers about it.

Tests confirmed she had the ability to smell the disease after she correctly identified six shirts worn by sufferers out of twelve in a blind test.

Now she has helped a team from Manchester find distinctive molecules that seem to be concentrated on the skin of Parkinson's patients, bringing the possibility that a test could be developed a step closer.

Mrs Milne said: “We had a very tumultuous period, when he was about 34 or 35, where I kept saying to him, ‘you’ve not showered. You’ve not brushed your teeth properly.

“It was a new smell - I didn’t know what it was. I kept on saying to him, and he became quite upset about it. So I just had to be quiet.”

But after Mr Milne was diagnosed with the disease she decided she had to speak out after noticing the smell on other Parkinson's sufferers.

The 67-year-old told the BBC: “We went to a Parkinson’s meeting and my nose just thought ‘wow’. 

“It’s a heavy, thick musky smell. Very different. People with Parkinson's and their families and their carers will tell you its there.

“As the Parkinson's got worse the smell got worse and it just became part of him. I had the sense not to nag too much.”

She now hopes the test will spare other families the pain of seeing loved ones succumb to the disease, which causes people to suffer uncontrolled tremors and paralysis. Mr Milne, who contracted the disease when he was 45, passed away two years ago.  

Parkinson's is difficult to diagnose as there is currently no lab test which can identify the disease, and there is is no cure.

Mrs Milne said: “It’s horrible watching your partner change like that. If we get the test right they will never get to that stage, because at that stage of diagnosis 60-70 per cent of the neural damage is done.

“We’re not going to find cure, it’s just not there at the moment. But to stop or alleviate it is just going to be tremendous. 

Prof Perdita Barran, an expert in chemical analysis who is trying to isolate the actual molecules that form the odour that Joy is able to smell, said that the work would not be possible without her help.

Prof Barran said: “It is very humbling as a mere measurement scientist to have this ability to help find some signature molecules to diagnose Parkinson’s. It wouldn’t have happened without Joy.

“For all the serendipity, it was Joy and Les who were absolutely convinced that what she could smell would be something that could be used in a clinical context and so now we are beginning to do that.”