In a new study funded by us, researchers have discovered new information about the role of a molecule found in chillis in reducing foot pain by healing damaged nerves. These results bring us closer to understanding how nerve damage in the feet caused by diabetes can be reversed, reducing the risk of serious foot complications.
People living with diabetes can be at a higher risk of nerve damage in parts of their body, known as neuropathy. If nerves are damaged in the feet, ulcers can develop, which can lead to amputations if left unchecked.
While symptoms of neuropathy can be treated, at the moment there aren’t any treatments that can reverse or halt the nerve damage.
For some people, neuropathy can also cause debilitating pain, which can be very difficult to treat with over-the-counter painkillers. People tend to be offered antidepressants to manage their pain, but this isn’t always successful and can come with a risk of side effects.
A hot topic in pain relief
Capsaicin is a molecule found in chillis, which gives them their fiery kick. It can also help to block pain signals from nerves when it’s applied to skin, making them less sensitive to pain. So capsaicin creams and skin patches – which stick to areas where nerves have been damaged – can be really helpful to reduce pain.
There’s also evidence that capsaicin can boost healing in some skin conditions like psoriasis. But we don’t yet know if capsaicin can help to treat the underlying cause of nerve pain, and how to reverse damage.
With our funding, a team of researchers at Imperial College London and Sheffield Teaching Hospitals recruited 75 people with diabetes and neuropathy. They investigated the effects of treating their feet with a patch containing 8% capsaicin (a licensed treatment for neuropathy called Qutenza), with one application for 30 minutes.
They wanted to figure out how the patch works to relieve pain, by looking at whether it could improve nerve damage over the course of three months.
50 of the participants had neuropathic pain, of which 32 were treated with the capsaicin patch and 18 received the current standard care for their pain. The other 25 participants didn’t have pain, but their neuropathy was still treated with the capsaicin patch.
During the study, participants were asked to keep a pain diary where they rated and described their pain, filled in questionnaires about their symptoms, and had their nerve sensitivity tested. They also gave samples of skin from their feet at the start and end of the study, and the researchers counted and analysed the nerves.
What the study found
After three months, the team found that those who’d been treated with the capsaicin patch reported that their pain had reduced significantly, compared to those treated with standard care.
Excitingly, everyone who’d been treated with the capsaicin patch appeared to have more new nerves in their skin samples at the end of the study. This suggests that part of capsaicin’s role in lowering pain is by helping to heal the nerves and triggering them to grow back.
The future of care for nerve damage
More research, including longer-term studies involving more people, is still needed before capsaicin patches could become part of routine care for people with neuropathy.
At the moment, capsaicin treatments are only available in specialist clinics for people with neuropathic pain. These results could spark changes in allowing more people to access capsaicin patches, helping them to reduce their pain by repairing damaged nerves.
These findings also help us understand for the first time how capsaicin patches work to address the symptoms of neuropathy by reversing the damage.
Being able to protect and regrow nerves would help people living with neuropathy to reduce their risk of developing more severe foot complications, while managing pain more effectively at the same time.
