Penicillin Allergy

Discovery of penicillin

Sir Alexander Fleming discovered penicillin in 1928. Fleming was a Scottish bacteriologist involved in the study of bacteria. For research and diagnostic purposes, he grew Staphylococcus (a gram-positive bacterium) in Petri dishes containing a solid medium with nutrients to support the growth of bacteria. One day Fleming noted there were no bacteria growing in a Petri dish that was next to a window and exposed to the elements. He also found that a mold called Penicillium was growing in the Petri dish instead of the bacteria. He rightly decided the mold Penicillium somehow be preventing the growth of Staphylococcal bacteria. Later he proved the mold was making a substance, which he named penicillin that was inhibiting the growth of bacteria. For this discovery, he gained a Nobel Prize in Medicine in 1945. In 1999, Time magazine named Fleming one of the hundred most important people of the twentieth century who changed the course of history.

You may not be allergic to penicillin!

Penicillin was the first antibiotic discovered by man. It led to the discovery of many more antibiotics. It saved the lives of millions of people all over the world during war and peace. Unfortunately with its widespread use rose the number of individuals who developed an allergy to it. With this development, doctors began using costlier and often less effective antibiotics for treating infections. This resulted in the development of drug-resistant bacteria such as MRSA (Methicillin Resistant Staphylococcus Aureus) which is causing havoc among both outpatients and inpatients all over the world. It is becoming apparent that something needs to be done to cut short this growing menace. Many people do not know that up to 70% of individuals who report penicillin allergy grow out of it about ten years after experiencing a convincing penicillin-allergic reaction. Their bodies just stop making allergic antibodies to penicillin because of penicillin avoidance. These people unnecessarily avoid penicillins and use costlier and less efficient antibiotics for the rest of their lives! A word of caution is necessary here. Please do not take penicillins on the assumption that you might not be allergic to it any longer. A negative penicillin allergy skin test to show that you are not allergic to penicillin is necessary before you could take penicillin again!

Types of penicillin-allergic reactions

Penicillin allergy is common and is the most common reported drug allergy in the Unites States. It affects 1-10% of people receiving the medication. It affects even people without other allergic tendencies such as hay fever and asthma. Penicillin could cause several types of allergic reactions. This ranges from a minor rash to life-threatening anaphylaxis. The humoral arm (IgE antibody) of the immune system arbitrates more immediate reactions such as hives, itching, swelling of different parts of the body and anaphylactic shock. The cellular arm of the immune system (nonIgE) arbitrates other types of reactions ranging from minor (rash) to more severe and life-threatening (Steven-Johnson Syndrome and Toxic Epidermal Necrolysis) reactions. If you had had experienced any of the later responses, then you should avoid penicillins and related medicines for the rest of your life!

Penicillin allergy skin tests are available now

Allergy skin tests to rule out IgE-mediated penicillin allergy are commercially available now. Allergy and Immunology specialists offer these tests in their offices in outpatient settings. You need to be off antihistamines and other potentially interfering medications before undergoing the test. Check with your doctor first before you stop any medications that you are taking currently. The test involves pricking your skin with Pre-Pen (penicillin allergy testing material) and Benzylpenicillin (an injectable form of penicillin). If the prick tests are negative for penicillin allergy, intradermal skin tests with the same reagents are carried out to be sure that you are not allergic to penicillin. If both prick and intradermal testing for penicillin allergy are negative, then your doctor may challenge you with oral penicillin tablets and keep you in the office for some time. The entire procedure should take no more than two to three hours to complete, and you should know by then if you could take penicillins in future or not! Some European Allergists believe that inclusion of amoxicillin (semi-synthetic penicillin) in the test improves the diagnostic accuracy of the test. A negative prick and intradermal skin tests using Pre-Pen and Benzylpenicillin alone can rule out penicillin allergy in 97% of patients. Please visit to learn more about penicillin allergy skin tests.

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