London: The sap from milkweed, a common garden weed, can kill certain types of cancer cells when applied to the skin.
It works on non-melanoma skin cancers, which affect hundreds of thousands of Britons each year.
They are triggered by sun damage and, although not usually fatal, can be disfiguring without treatment, the British Journal of Dermatology reports.
The plant has been used for centuries as a traditional folk medicine to treat conditions such as warts, asthma and several types of cancer.
But for the first time a team of scientists in Australia has carried out a clinical study of sap from Euphorbia peplus, which is related to Euphorbia plants grown in gardens in Britain, according to the Daily Mail.
The study of 36 patients with a total of 48 non-melanoma lesions included basal cell carcinomas (BCC), squamous cell carcinomas (SCC) and intraepidermal carcinomas (IEC), a growth of cancerous cells confined to the outer layer of the skin.
Patients had failed to respond to conventional treatment including surgery, or they refused or were unsuitable for surgery because of their age.
The patients were treated once a day for three consecutive days by an oncologist using a cotton bud to apply enough of the E.peplus sap to cover the surface of each lesion.
The initial results were impressive. After only one month, 41 of the 48 cancers had completely gone. Patients who had some of the lesions remaining were offered a second course of treatment.
After an average of 15 months following treatment, two thirds of the 48 skin cancer lesions were still showing a complete response.