WEDNESDAY, March 21 (HealthDay News) -- Most sinus infections are caused by viruses and should not be treated with antibiotics, which target bacteria and are useless against viruses, new expert guidelines state.

About 14 percent (one in seven) of people are diagnosed with a sinus infection each year, and sinus infections remain the fifth leading reason for an antibiotic prescriptions. However, between 90 percent and 98 percent of the infections are caused by viruses, which are not affected by antibiotics, according to the Infectious Diseases Society of America (IDSA), which released the new advisory on Wednesday.

IDSA noted that the inappropriate overuse of antibiotics is encouraging the development of tough-to-treat, drug-resistant bacteria or "superbugs."

An inability to determine which germ is behind a particular case of sinusitis often leads to inappropriate prescribing, one expert said.

"There is no simple test that will easily and quickly determine whether a sinus infection is viral or bacterial, so many physicians prescribe antibiotics 'just in case,'" Dr. Anthony Chow, chair of the guidelines panel and professor emeritus of infectious diseases at the University of British Columbia, Vancouver, said in an IDSA news release.

"However, if the infection turns out to be viral -- as most are -- the antibiotics won't help and in fact can cause harm by increasing antibiotic resistance, exposing patients to drug side effects unnecessarily and adding cost," Chow noted.

Most sinus infections -- which can cause uncomfortable pressure on either side of the nose and last for weeks -- develop during or after a cold or other respiratory infection. But other factors, such as allergens and environmental irritants, may play a role.

Experts agreed with the new guidelines.

The recommendations "recognize two common problems with previous guidelines: bacterial rhinosinusitis is overdiagnosed and antibiotic resistance among common sinus pathogens has increased significantly," said Dr. Richard Lebowitz, an otolaryngologist at NYU Langone Medical Center and associate professor at the NYU School of Medicine, in New York City.

He believes the recommendations are an "improvement" on prior guidelines, but there are also "potential pitfalls" if a diagnosis isn't clear. "The gold standard [for diagnosis], and the only way to avoid misdiagnosis and improper treatment, is with endoscopy-based diagnosis and culture-directed antibiotic therapy," Lebowitz said.

Another expert noted that there is often "confusion" in distinguishing viral from bacterial sinusitis, because symptoms are often similar. Still, "most patients want some kind of treatment when they go to the doctor," said Dr. Linda Dahl, an ear, nose and throat specialist at Lenox Hill Hospital in New York City. "The new guidelines establish updated recommendations for treating these patients in the primary care setting," she said.

The IDSA guidelines also recommend treating the small fraction of sinus infections caused by bacteria with amoxicillin-clavulanate, rather than the current standard of care, amoxicillin. This recommendation was made due to increases in antibiotic resistance as well as the widespread use of pneumococcal vaccines, which have altered the pattern of bacteria that cause sinus infections, Chow explained.

The guidelines also recommend shorter antibiotic treatment times (five to seven days) for adults with bacterial sinus infections.

Patients with either bacterial or viral sinus infections should avoid decongestants and antihistamines, IDSA added. They are not helpful and could make symptoms worse, the IDSA team said. Nasal steroids may help people with sinus infections who have a history of allergies. Nasal irrigation using a sterile solution in the form of spray, drops or liquid may help relieve some symptoms, according to the guidelines.

Dahl said she found the guidelines, "very useful and in line with the way I practice with a few exceptions." On the issue of decongestants, she said, "I advocate for decongestants in relieving symptoms and preventing viral infections from turning into bacterial infections. The sinuses are literally holes in our skull that produce mucus. If the lining of the sinuses becomes inflamed the mucus cannot drain and can harbor bacterial growth. By keeping the passages open (with decongestants and nasal sprays) the sinuses can heal more quickly."

Other treatments might help some patients, Dahl added, including "manual suctioning of the sinuses, topical antibiotics [in certain cases], and anti-inflammatories such as fish oil that are quite helpful and speed recovery. And most importantly, rest and good sleeping habits."

More information

The U.S. National Institute of Allergy and Infectious Diseases has more about sinus infection.