The accidental discovery was made by scientists looking for a way to improve treatment for blood cancer patients
A wonder cream could bring relief to millions of patients with eczema, arthritis and a form of alopecia.
All three conditions are caused by a problem where the immune system targets the body’s healthy cells.
But scientists looking for a way to help blood cancer patients have stumbled on a way to switch off that response.
Dr Aurore Saudemont, of the Anthony Nolan Research Institute, said: “This accidental discovery could offer a major breakthrough.
“These findings could eventually lead to treatments that eradicate symptoms of eczema, rheumatoid arthritis and even alopecia areata without causing major side effects.
This could be life-changing for patients.”
More than six million Britons have eczema, which causes dry, itchy skin.
Another 400,000 people suffer crippling joint pain with rheumatoid arthritis.
And a million have alopecia areata, which leads to patches of hair loss.
But the cream, which could be available to test within three years, will not cure hereditary baldness in men.
In response to the findings, Amy Johnson, of charity Alopecia UK, said: “The psychological impact of alopecia areata can be huge.
“Many find it very difficult to adjust to the change in their appearance that hair loss brings.
“We are always interested to learn of medical research into other conditions that could have benefits for people with alopecia areata.”
The Anthony Nolan experts were looking for a way to cure a complication that affects 80% of stem cell transplant patients.
It happens when donated cells see existing cells as foreign and start to attack them.
Researchers made a breakthrough when they found a protein in umbilical cord blood that stops a pregnant mum’s immune system attacking the unborn baby.
They studied cord blood donated by new mums, while stem cells were harvested from the umbilical cords.
Dr Saudemont added: “It is very exciting to discover that a product usually discarded could be so valuable.”