The British analysis of six prior studies found that the sprays confer only a small degree of benefit, and only after being taken for three weeks at relatively high doses.

The disappointing observation comes amid growing public health concerns that the more common use of antibiotics for short-term sinusitis symptoms is both ineffective and potentially dangerous because the drugs contribute to bacterial resistance.

"Looking at all the trials together, we found that nasal steroids seem to give a small benefit for patients with acute sinusitis," said study co-author Matthew Thompson, a senior clinical scientist in the department of primary care health sciences at the University of Oxford, in England. "In fact, they work about as well as antibiotics do."

"When we compared patients who were given steroid nasal spray with those who were given an [inactive] spray, we found that patients given the steroid spray got better faster," he added. "However, although we see this effect after taking the spray for 14 days, the big difference only occurs at 21 days. We also found that a larger dose of the nasal steroids worked better than a lower dose."