Many people still do not know which infections can be treated with antibiotics, and doctors may not be warning their patients about the hazards of taking the drugs too often, a U.K. study suggests.

Primary care doctors dispense most antibiotics, so they need to do a better job of educating patients about when antibiotics are really needed and the consequences of overusing the drugs, researchers say.

"The more you take antibiotics the more bacteria in your body will become resistant, so the next time you really need an antibiotic for pneumonia or a kidney infection, for example, it may not be as effective," said lead author Cliodna McNulty, head of the Primary Care Unit at Public Health England in Gloucester.

In the U.K., 74 percent of antibiotics are prescribed by general practice physicians, the researchers write in the journal Family Practice. Many patients may request the drugs for viral infections, which are not treatable with antibiotics, they add.

Antibiotics work on bacterial infections, but not on viruses. Antibiotic resistance occurs when the bacteria causing common infections evolve so that the drugs no longer work on them.

"Most coughs, colds, sore throats, flu and sinus infections are self-limiting and will get better on their own. Antibiotics only improve symptoms by about 8-12 hours," McNulty told Reuters Health by email.

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Antibiotic resistance is one of the greatest health threats worldwide and leads to longer hospitalizations, higher medical costs and death, according to the World Health Organization.

The researchers used an independent research agency to conduct a face to face survey of randomly selected homes across England. The 1,625 adult participants answered questions about their use of antibiotics, whether their doctors gave them information about antibiotics in general and about resistance in particular, and whether they trusted their doctors' knowledge.

Just over one third of participants said they had been prescribed an antibiotic in the past year.

Among those with prescriptions, 62 percent of people with throat infections, 60 percent with sinus infections, and 42 percent of those with a cough or cold took antibiotics, although all these conditions tend to be caused by viruses.

Asked whether most coughs, colds and sore throats get better on their own without the need for antibiotics, 86 percent of survey participants agreed, but only 44 percent correctly answered that antibiotics treat bacterial and not viral infections.

Just 45 percent of participants agreed that healthy people can carry bacteria that are resistant to antibiotics.

Two-thirds of participants remembered getting advice from their doctors about their infection or about antibiotics, but only 8 percent said they got information about antibiotic resistance.

Eighty-eight percent of subjects trusted their doctors to decide if they needed antibiotics.

"It's extremely important for providers to share information with patients and parents about the benefits and harms of using antibiotics," said Dr. Lauri Hicks, director of the Office of Antibiotic Stewardship at the U.S. Centers for Disease Control and Prevention.

Doctors should talk to patients about when antibiotics are and are not needed and about possible issues with antibiotics like allergic reactions and antibiotic resistance, said Hicks, who was not involved in the study.

"Doctors are often under a lot of time pressure, so doctors can also provide resources to guide patients, like hand-outs and, if appropriate, websites that have more information about appropriate antibiotic use and antibiotic resistance (e.g. www.cdc.gov/getsmart)," Hicks told Reuters Health by email.

McNulty said that antibiotics can be life-saving drugs for serious infections, but they are not needed for colds or flu-like illnesses. She noted that having a stuffy or runny nose with your other symptoms is often a sign that antibiotics are not needed.

"Trust your GP or nurse to prescribe antibiotics when you need them. Do ask them to share information with you about how you can self-care, how long the symptoms should last and when you should return (if symptoms are not improving or you are feeling worse)," McNulty said.