Their bodies have become their prison cells.
For some, the only option is to be confined to a bed, cloaked in darkness and silence, the smallest noise or light unbearable. For others, there is little, and sometimes no, escape from the constant pain and fatigue which gnaws at them. Sometimes for years.
These are just some of the debilitating symptoms affecting some sufferers of chronic immunological and neurological conditions such as chronic fatigue syndrome and fibromyalgia.
Researchers estimate chronic fatigue syndrome, also known as myalgic encephalomyelitis (ME), affects more than 200,000 Australians.
They are illnesses which sufferers say are often misunderstood and even more difficult to diagnose.
Monday, May 12, is International Awareness Day for Chronic Immunological and Neurological Diseases. Patients, medical experts, support groups and researchers are seeking to highlight the plight of sufferers and lead a push for more research.
Professor Marshall-Gradisnik, who heads up the National Centre for Neuroimmunology and Emerging Diseases, said research into illnesses such as Chronic Fatigue Syndrome was critical.
"There's no defined pathology of the illness which means that biomedical research ... is paramount because without finding out the actual mechanism of the illness, then it's very hard to then introduce a treatment," she said.
The NCNED is dedicated to researching the interaction between the nervous system and the immune system. A specialised chronic fatigue syndrome clinic to treat CFS sufferers is set to open next month .
Bob Townsend, president of ACT ME/Chronic Fatigue Syndrome Society, said diagnosis was also a difficulty because it is "often done through a process of elimination".
He said the society had about 120 members, which included a number of young people and teenagers.
Mr Townsend said sufferers could often feel isolated, making it important for them to have access to information and support.
Asked whether people with chronic fatigue syndrome and fibromyalgia could lead "normal" lives, he said they could if "they manage their symptoms, are aware of their limits and don't try to push themselves too hard".
Amanda Kelly, chief executive of ME/CFS Australia Victoria, said the illness had the potential to turn sufferers' lives upside down.
"You can go from being an active, functional member of society to someone who cannot leave a darkened room, can't stand noise and may even be sensitive to the sheets you're lying on," she said. "There are also cognitive difficulties with it, which is commonly called brain fog, there is a large number of digestive problems as well that people can get with it. It can have a severe impact and it's particularly difficult with children."
Ms Kelly said there was no proven treatment for chronic fatigue syndrome.
Buildings and landmarks across Australia, including AAMI Park in Melbourne and Griffith University's Health Centre on the Gold Coast, and internationally, including Niagara Falls, Suan Juan Capital in Puerto Rico, Spinnaker Tower in England, will be lit up in blue, purple or green in support of International Awareness Day.
For more information about chronic fatigue or ACT ME/Chronic Fatigue Syndrome Society, visit: http://www.mecfscanberra.org.au/. Information about International Awareness Day can be found at: http://www.may12th.org/.