A new CDC study finds a third of all antibiotic prescriptions are unnecessary.

FOX's Anna Welles reports: 

CDC researchers say at least 30 percent of the drugs are prescribed for common colds, sore throats, bronchitis and sinus and ear infections, which don't responded to antibiotics.

The study says the unnecessary prescriptions put patients at risk of developing allergies. The concern is overuse could lead to antibiotic resistance.

CDC director Tom Friedan says if we continue down the road of inappropriate use we'll lose the most powerful tool we have to fight life threatening infections.

Anna Welles, FOX News.