A practitioner of Chinese medicine has pleaded guilty to selling a banned substance to a woman who went on to develop kidney failure and cancer.
Ying "Susan" Wu, 48, of Holland-on-Sea in Essex, has been on trial at the Old Bailey for selling pills containing aristolochic acid to a civil servant.
The judge said he accepted Ms Wu had not meant to harm, and that the case highlighted the need for regulation.
Ms Wu has now been given a conditional discharge.
Patricia Booth, 58, took the pills, bought at Chelmsford's Chinese Herbal Medical Centre, for over five years. She was in her mid-40s when she first sought help from the centre in 1997 for stubborn patches of spots on her face.
The Old Bailey heard the products had been advertised as "safe and natural".
But they contained a substance - aristolochic acid - which when she was first sold them, should only have been given under prescription, and which was later banned.
Traditionally this would be used maybe once or twice by a doctor who would know about its toxicity, but sometimes it might get into a formulation which is then used by somebody who doesn't have this wealth of experience
Professor Monique Simmonds
The court heard Mrs Booth became ill months after she stopped taking the pills. She was diagnosed with kidney failure, and later with cancer of the urinary tract - both allegedly caused by the pills.
The grandmother, who used to manage a government office of up to 60 people, currently goes to hospital three times each week for dialysis.
She had told the court that she had been advised to take about 30 tiny brown tablets three times each day, returning to the shop every two weeks to buy up to three bottles at a time. She became friendly with Ms Wu, who was employed at the shop as a "Chinese doctor" until it closed in 2003.
Ms Wu, who had initially denied the charges, pleaded guilty to selling prescription only medicines without authorisation and to selling a banned substance.