A high-dose shot of a common asthma drug, once a month, has been found to be highly effective in treating teens and adults chronically afflicted with severe, itchy rash, says a new study.

Known as omalizumab, the drug was tested on 323 people at 55 medical centres for whom standard antihistamine therapy failed to quell underlying, allergy-like reaction, known as chronic idiopathic urticaria or chronic spontaneous urticaria.

"Physicians and patients may now have a fast, safe and well-tolerated treatment option to consider before prescribing even more antihistamines, which can be highly sedating," says Sarbjit (Romi) Saini, Johns Hopkins allergist and immunologist, and study co-investigator, the The New England Journal of Medicine reports.

The study, from 2009 to 2011, involved mostly women aged between 12 and 75 years. Each was randomly assigned to take one of three dosing regimens of omalizumab, or placebo, after which they were monitored through regular checkups for four months, according to a Johns Hopkins statement.

All of them had chronic hives (itchy bumps on the skin) and rash for at least six months, with many having suffered from the condition for more than five years.

"Patients suffering with this condition need more and better treatment options because chronic hives and rash are profoundly hard to treat and can be very debilitating," says Saini, associate professor at the Johns Hopkins University School of Medicine.

Saini, who has studied omalizumab since 2005, points out that fewer than half of those treated respond to traditional drug treatments with antihistamines. Saini says the new study results offer substantial evidence that this first injection treatment option not only works, but does so more safely than other drugs.

These findings were presented at the annual meeting of the American Academy of Allergy, Asthma and Immunology in San Antonio, Texas.