By Dr. Dave Hnida

(CBS4) – Think you’re allergic to penicillin?

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Well, maybe not. Or actually, probably not.

A new study suggests that about 90 percent of people who think that they are allergic to penicillin-  are not truly allergic, and can safely and effectively use the drug.

The research comes from the American Academy of Allergy, Asthma, and Immunology and takes a fresh look at one of the first antibiotics to ever be used (sulfa is the other). The drug was discovered in 1928.

Years ago, penicillin pretty much worked against everything, and was one of the commonly prescribed medicines in the world. But over time, its effectiveness wore off, and we had to turn to more powerful, more expensive, and more side effect prone antibiotics.

Adding to the problem was the idea that a lot of people had, or thought they had, reactions to penicillin, so they avoided it like the plague. The actual number: about 10 percent of Americans believe they are allergic.

But it turns out that things have changed over the years.

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First, experts now believe that many of the so-called allergic reactions to penicillin were not really allergic reactions. Meaning, something like a stomach ache after taking the pill wasn’t really an allergy, but simply that the drug didn’t agree with the system. Or that the rash that developed while using penicillin was not really an allergy, but instead a rash from the infection itself or a non-allergic sensitivity to the antibiotic.

Second, and perhaps more significant, is the concept that it’s possible to outgrow your allergy to penicillin. It’s like being allergic to pollen or having asthma in your younger years, then having the problem simply go away as you get older.

All in all, that 10 percent figure of allergic Americans is probably more like 1%.

So how can you tell if you think you are allergic to the drug, but want to know if you aren’t.

Well, this is one of these “don’t try this at home” deals. It’s possible for us to test you in the office to see if you truly still, or ever, have had an allergy.

It involves a skin test with a small amount of penicillin, as well as a placebo, to see if you react. Then, if you don’t, you take a very small amount of penicillin orally to see if it causes a problem. The whole testing process takes about three hours, and is best performed by an allergist

If you’re truly allergic, it’s a great deal, since we now can go back to a basic, simpler medication if you need something. And when I think of all of the people I know who can’t take other antibiotics because of allergies, or are on medicines that don’t mix well with the more potent medicine, being able to turn back the clock to old-fashioned penicillin is a nice alternative.

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Dr. Dave Hnida is CBS4’s Medical Editor. He blogs about the latest studies and trends in the health world. Read his latest blog entries, check out his bio or follow him on Twitter @drdavehnida.