Strange Rash Is Really Harmless

Posted on Wed., July 1, 2009
By Veda Bhatt, M.D.

RECENTLY, A 30-year old woman came to my office with a pink, oval-shaped spot on the side of her stomach. She was worried it might be skin cancer.

Just by looking at it I could tell it was not cancer, but I wasn't sure what it was. I suggested she try hydrocortisone cream and return if the rash continued or worsened. Within a week, she was back in my office because the spots had spread to her whole abdomen, chest and back.

Although she was now even more worried, I could tell she had a relatively common skin disorder called pityriasis rosea. This is a rash that affects roughly 500,000 people, mostly young adults, each year in the United States.

Though the cause of pityriasis rosea is not known for certain, most doctors think it is caused by a viral infection, possibly the human herpes virus.

However, signs of a viral infection—such as fever, or blisters and ulcers in some cases of herpes—are generally not present.

The rash typically begins with a 1- to 2-inch pink, irregular patch on the chest or back. At that point, it can be mistaken for other skin diseases, such as ringworm or eczema.

Many people report symptoms similar to a cold before the appearance of the first patch—tiredness, headache, sore throat and nausea.

Several days after the initial spot, more similar but often smaller spots will appear. The spots, which are pink, flat and usually irregular in shape, are generally about ¼- to 1-inch in diameter. They often spread all over the chest, stomach and back, and may even extend to the arms and legs.

The spots usually follow the lines of the skin, and as a group can form in an arc down and out on the back to form a "Christmas tree" shape (narrow at the top, wide at the bottom). Occasionally, the spots will spread to the neck, but hardly ever to the face.

To help reduce the itching and save a trip to the doctor (but not, unfortunately, to speed up recovery), try the following:

Use calamine lotion and skin moisturizers to reduce dryness.
If the itch persists, try over-the-counter hydrocortisone cream or Benadryl (pills or syrup).
Take lukewarm or cool showers or baths, using gentle soap.
Wear cotton and silk fabrics.
Avoid sweating, which may irritate the rash.

Pityriasis rosea almost always fades without treatment within six to eight weeks.

It is not caused by a fungus, so antifungal creams don't help.

But there is a fungal rash, called tinea versicolor, that may cause spots which can look similar to pityriasis rosea. The spots of tinea versicolor are usually more circular and appear only on the upper chest, back and neck. This fungal rash often seems to recur year after year during the summer.

Fortunately, pityriasis rosea is seldom contagious, and generally affects only one member of a family. It returns to the same person less than 3 percent of the time.

If your rash does not go away within three months, contact your doctor. Although time is the only known cure, steroid creams or light therapy can sometimes help.

Bhatt practices family medicine at the Contra Costa Regional Medical Center in Martinez.