A man was left with large burns across his body after a dermatology clinic gave him a treatment for a different patient, the health watchdog has found.
He had been undergoing a regular course of phototherapy at the clinic to treat his eczema, said the Health and Disability Commissioner's report.
An hour after he left the clinic, the man received a call from the dermatologist advising that he had received the wrong treatment.
The dermatologist told the man an employee, "had opened a folder for a different patient and loaded their treatment", which was much stronger than the man's usual treatment.
The dermatologist apologised for the mistake and told the man that he would develop bad burns, for which he prescribed aspirin and a topical steroid cream.
By the next morning the man had developed several blisters on the front of his body.
Over the next few days, the blistering worsened, covering most of the front of the man's body, from his chin to his waist.
The pain rendered him bed-bound and unable to carry out daily tasks, and he had to take two days off work.
The clinic in their investigation of the mistake found two errors were made.
The first was that the employee who opened the man's profile in the phototherapy system, accidentally clicked on a different patient with the same first name after they had confirmed the profile for the correct patient.
The second error was that the employee did not enter the patient's phototherapy dose into the clinic's practice management software until after the man had completed his treatment.
If it had been entered prior, the system would have generated an alert if the dose is more than 20 percent higher than the previous dose.
The health and disability commissioner found the clinic breached the Code of Health and Disability Services Consumers' Rights.
Deputy health and disability commissioner Dr Vanessa Caldwell commended the clinic on its prompt and transparent investigation into the mistake.
"The changes to the clinic's processes were specific and appropriate to reduce the risk of the same error happening again."
However, Caldwell found the clinic breached Right 4 of the Code, for failing to provide services to the man with reasonable care and skill.
She said the injury was avoidable and should not have occurred.