Another mysterious and one of the commonest of skin diseases is psoriasis. It is probably not well known to the general public as it usually persists throughout the patient’s life, so it is not brought forward as a subject of conversation. In fact, being rather disfiguring, it is kept secret as much as possible. It consists of scaly patches on the skin, the more common locations being the back of the arms, the front of the legs, and the body. Fortunately the face is frequently spared.

Psoriasis starts as minute spots which grow and merge into large areas, occasionally covering the whole back or even the whole body. Although the patient is usually symptom-free, being bothered only by the disfigurement and the untidiness of the scales flaking off, nevertheless severe cases may feel run down and even quite sick. Fortunately the scaling has a tendency to clear up at times, especially in warm weather, but it will break out again as cold temperatures return.

The cause is unknown. No evidence has been found of bacteria associated with the eruption, and the disease is not contagious. Some of the other ailments of the skin may be confused with psoriasis and the treatment proper for them would be bad for this condition. Therefore it is important that a competent skin specialist make the diagnosis. Probably sooner or later all such cases are seen by specialists, for even the most ignorant or indifferent will not forever accept with equanimity such unpleasantness.

There have been many methods of treatment, some of which give good results. Medicines taken into the system have in general amounted to little. It is fortunate if they do no harm. Vitamins, of course, have been tried. Massive doses have generally been considered necessary by their users, and in such amounts they are not at all innocuous. Experiments with diet may seem to help or to coincide with improvement. Apparently there are no good rules for this.

External applications give the best means of relief. They have to be handled with care and according to the state of the disease. It would be useless here to give a list of the drugs used. Self-medication is dangerous either with drugs or ultra-violet light from lamps or sunlight. And the relief is temporary. Almost always there are bound to be recurrences. X-ray has been used, but in a chronic recurring trouble like this one it should be seldom resorted to, for cancer is a distinct danger where these rays are repeatedly used on unhealthy skin.

All authorities agree that there is no definite cure or permanent alleviant. I do not believe that any good physician, having treated a case of psoriasis, ever assures the patient that he will no longer have the disease. In fact, I believe that he will tell him that he must expect to have it return later. It fluctuates so much, occasionally disappearing for a time that false hopes are bound to arise. Occasionally, but rarely, it has disappeared and not returned. Nobody knows why. Perhaps the period of remission has just happened to exceed the patient’s life span.