Ray, 69, has been chairman of The Psoriasis Association for the last 33 years. He's lived with psoriasis since he was 14 and continues to treat it with coal-tar medication.

"It was 1955 and I was a 14-year-old schoolboy when my psoriasis appeared quite suddenly. I wasn’t sure what it was and didn’t have any experience of it in my family. The GP just said it might go away.

"Within about three weeks it had begun to spread. It was guttate psoriasis, so I had a pattern of little raindrop-shaped red spots that were slightly raised. This quickly spread to plaque psoriasis, and the patches began to get bigger. By then, it was scaling profusely.

"It was one of those conditions that no one knew much about. Doctors said I would just have to learn to live with it.

"I eventually got referred to a district general hospital, where I was treated with coal-tar baths and ointments. In those days it was awful stuff. It had a powerful smell and was very staining. My mother helped with the treatment and endured the laundry. I had my own linen and bed wear.

"The psoriasis came and went a little but was always present. Because of the ointments and shampoos I would smell like a newly paved road, and when it rained my hair gave off this peculiar odour.

"The psoriasis was on my body and hands but not on my face, and I could manage my scalp by combing my hair a certain way, but people always thought I had dandruff. The psoriasis improved in sunlight, so my condition was better in the summer, but it would always return.

"So I would go to hospital to have my psoriasis treated with ultra-violet light, which gave me a rather dark winter tan. This was an unusual appearance in those days, as we were an ordinary family and there was no jetting off to beaches or ski resorts. I actually received racial abuse a couple of times from people who thought I was Indian or Maltese.

"When I was 16, I wanted to join the Navy. After a few months of competing I managed to get through to the final stage, which was a medical examination. But then I was rejected. I was told I had a lifelong disease that was inappropriate for the conditions of service. I completely had to rethink what I was doing.

"In 1960, steroid medications came in. I would apply the steroids and then put on an occlusive polythene suit, which covered my trunk, arms and legs. I would be sweating underneath it and I smelt bad, an experience I wouldn’t wish on my worst enemy, even though it was a great innovation at the time.

"My psoriasis still flares up every now and then. Just over a year ago, it went wildly wrong. My legs were swelling and I was in a really bad way, so the doctors said I might have to go into hospital. I ended up taking ciclosporin, which suppresses your immune response. It restored me back to my normal psoriasis state.

"I now use a mild coal-tar preparation twice a day on the affected areas. It’s OK and doesn’t smell quite as bad as it used to. My wife, who I’ve been married to since 1965, has helped me with this virtually every day of our marriage. I have to get up extra early to allow enough time to apply the treatment and get to 9am meetings, and my wife gets up with me.

"I imagine there are hundreds of thousands of people who have to go through this regimen."