Conservators at Britain's Textile Conservation Centre - based at Hampton Court - have found the remains of Merrick's saliva, nasal mucus and probable skin grease on the original hat and veil which he used to hide his deformed face from the world.
Discussions between the centre and police forensic scientists indicate that it may be possible to extract DNA from the saliva and this could potentially be used to reveal what disease Merrick suffered from.
Until 1986, doctors believed that Merrick had suffered from a condition known as neurofibromatosis, but since then some specialists have claimed that the deformation of his body was the result of a totally different disease called Proteus Syndrome.
Potentially, neurofibromatosis could be identified by DNA tests on skin fragments normally found in saliva. This may be possible despite the fact that the material is old and very dry.
If, on the other hand, the DNA evidence totally rules out neurofibromatosis, then Proteus Syndrome would become the most likely cause of Merrick's condition. A positive DNA test for Proteus Syndrome itself does not exist yet - but may be developed in the future. Unlike neurofibromatosis, Proteus Syndrome is not hereditary, but both involve genetic changes.
Neurofibromatosis is a hereditary condition involving the overgrowth of the coverings of the nerve channels. One in 3,000 people in Britain suffer from it, mostly in a very mild form. It only manifests itself more seriously in one in three million. These days, serious growths can often be removed surgically.
Proteus Syndrome is an extremely rare non-hereditary condition, caused by a malfunction in cell growth, in which bone and flesh tissue overgrow in localised areas of the body. It was first recognised in its severe form only 16 years ago and only 80 cases have been recorded worldwide. In its mild form, it has been fully recognised only since 1992.
The saliva remnants on the Elephant Man's veil are probably the only way of solving the mystery of his disease.
For although his skeleton still survives as a specimen in the London Hospital Medical College attached to the Royal London Hospital, in Whitechapel, east london, its use as a source of DNA was almost certainly destroyed in 1890 when the bones were boiled and then bleached with peroxide by Thomas Horrocks Oppenshaw, the London surgeon who was otherwise famous for his massive collection of gallstones and other calculi, and his role in helping with the Jack the Ripper murder investigations.
The conservation work on the Elephant Man's hat and veil - also owned by the medical college - has just been completed by a final year student, Michelle Harper, at the Textile Conservation Centre.
Moves by scientists at the medical college to assess the possibilities of using DNA to solve the mystery of the Elephant Man started last year - before the saliva was discovered on the veil.
Joseph Merrick, alias John Merrick, was born in Leicester in 1862 and died in 1890 from asphyxia caused by the pressure of his giant head on his windpipe.
Merrick was well educated, composed poetry and regularly wrote letters to friends and family.
He suffered terribly from his deformities. His right wrist was 30cms (12ins) in circumference, while his head was 90cms (35ins) in circumference.
From 1884 to 1886 he was the star of a freak show, from which he received half the income - and in 1886 he was admitted to the London Hospital as a resident patient, his upkeep paid for by public appeal.
His black velvet peaked cap and attached grey woollen veil complete with rectangular eye slit will be on show as part of a public display of conserved textiles at the Courtauld Institute of Art, central London, for the next three months.
Those other possessions which survived his death - his black cloak and slippers - were kept by the London Hospital Medical College, but were lost earlier this century.
Samples of his deformed skin and other tissues - preserved in alcohol - were destroyed during the Second World War; but the skeleton and plaster casts of his head and limbs are still kept for medical research at the college, but are not accessible to the public.
"If appropriate funding can be obtained we will attempt to get DNA from the saliva," said David Nunn, the college's senior official responsible for medical specimens.