A national shortage of commonly used medication is causing concern among doctors and parents this flu season.

Amoxicillin is one of the most commonly prescribed pediatric medications. The antibiotic is used to treat ear infections, bronchitis and strep throat. Recently, it's been hard for physicians to prescribe it because there's a limited amount on the shelves.

"This is something we haven't seen in a few years. Other drugs and other problems we've heard about, but amoxicillin is very available. It's not a hard substance to make,” says pediatrician Dr. John Zaso.

Zaso says a significant uptick in respiratory diseases this season may be to blame.

"It doesn't seem like it's from the production side. From what we've been told by the manufacturers -- I think there's a huge demand for it right now,” he says. “I think that's because of the masking for two years, everyone's masks are off now, and now we're getting all these respiratory illnesses because their immune systems are not revved up yet."

Zaso says parents shouldn't worry because there are other alternatives.

"There are other concentrations of amoxicillin available so it would just be up to the physician to recalculate the dose with a different strength and if that's tight -- then go with a different antibiotic,” he says.

The U.S. Food and Drug Administration says it is working with pharmaceutical companies to address the shortage.