Doctors often prescribe an oral corticosteroid, like prednisone, along with an antihistamine to treat mild itchy rashes. But steroids, which carry risks, even in the short term, may not be needed.

Researchers randomly assigned 100 adults with itchy hives to have daily treatment with either an antihistamine (levocetirizine, brand name Xyzal) and prednisone, or the antihistamine and a sugar pill. The study is in the Annals of Emergency Medicine.

Two days later, 62 percent of the patients in the prednisone group reported that the itching had gone away, but so did 76 percent of those in the placebo group. The rash had disappeared completely in 70 percent of the prednisone group and in 78 percent of the placebo group.

There were no differences in adverse effects between the two groups, and no differences in the number of relapses after the treatment period. The authors acknowledge that the data depends on self-reports from patients who were not examined clinically.

According to the lead author, Dr. Dominique Lauque, a professor of medicine at the University of Toulouse III in France, one reason doctors still use steroids to treat rash is that patients demand them. But, he said, better to avoid them when the rash is mild.

More serious allergic reactions may require steroids, he continued, but in mild cases, “I prescribe one of the new antihistamines.”