Penicillin Allergy: Things You Should Know

NOTE: This article is over 3 years old and may not reflect current information, despite the page being updated. It may still be useful for research but should be verified for accuracy and relevance.

Published: 2016-12-18 - Updated: 2019-11-05
Author: Allergy and Asthma Network | Contact: AllergyAsthmaNetwork.org
Peer-Reviewed Publication: N/A
Library of Related Papers: Allergies and Allergens Publications

Synopsis: Facts and information regarding penicillin allergy, being allergic to penicillin causes an abnormal reaction of the immune system to the antibiotic drug penicillin. Up to 10% of the population report being allergic to penicillin, according to the U.S. Centers for Disease Control and Prevention (CDC). Anyone who believes they are allergic to penicillin because they had a reaction years ago should undergo testing with a board-certified allergist.

Main Digest

Penicillin was originally discovered in 1928 by Scottish scientist Alexander Fleming. It wasn't until 1942 that it was used to treat infections in humans.

Today, there are several enhanced families of penicillin effective against additional bacteria they include:

Antistaphylococcal penicillins
Aminopenicillins
Antipseudomonal penicillins

Penicillin was considered a wonder drug when it was first introduced in 1928 - and it has revolutionized medicine ever since. We can now treat infections that used to be a death sentence.

Related Publications:

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Sir Alexander Fleming (6 August 1881 - 11 March 1955) was a Scottish biologist, physician, microbiologist, and pharmacologist. His best-known discoveries are the enzyme lysozyme in 1923 and benzylpenicillin (Penicillin G) from the mould Penicillium notatum in 1928, for which he shared the Nobel Prize in Physiology or Medicine in 1945 with Howard Florey and Ernst Boris Chain. Sir Alexander Fleming wrote many articles on bacteriology, immunology, and chemotherapy.

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What if You Believe You are Allergic to Penicillin?

You may still have options.

Up to 10 percent of people report being allergic to penicillin, according to the Centers for Disease Control and Prevention (CDC). However, up to 90% of this group may not actually be allergic to penicillin. Serious allergies only occur in about 0.03% of the population. Persons who are allergic to penicillin are usually given a substitute known as cephalosporin C because of its functional groups.

"Understanding penicillin allergy is important," says Tonya Winders, president and CEO of Allergy & Asthma Network, the leading nonprofit patient education organization for people with asthma and allergies. "It kills 400 people a year. However, studies show many people who believe they are allergic to penicillin really are not. This mistaken belief leads to higher drug costs, inferior medical treatments and possible antibiotic resistance. If you think you are allergic to penicillin, see a board-certified allergist for testing. Don't wait until you're in a medical crisis."

Here are the top things the Network wants you to know about penicillin allergy:

Penicillin allergy is serious and can be life-threatening.
Anyone who is allergic to one type of penicillin should be considered allergic to all penicillins and avoid the entire medication group. This group includes more than 15 chemically related drugs, such as ampicillin, amoxicillin, amoxicillin-clavulanate and methicillin. If you are allergic to penicillin, talk with your physician and pharmacist before taking any new medicine you are prescribed to confirm that it's not penicillin-based. Ask whether you should carry an epinephrine auto-injector, the only treatment proven to stop anaphylaxis, a life-threatening allergic reaction.
Penicillin allergy may not be a lifelong condition
A reaction in childhood does not automatically predict a reaction as an adult. Only about 20 percent of people will be allergic to penicillin 10 years after their initial allergic reaction if they are not exposed to it again during this time period.
Penicillin allergy symptoms may include hives, swelling of the mouth or throat, difficulty breathing or dizziness.
Hives that suggest true allergy are raised, intensely itchy spots that may appear and change within hours - but not all skin rashes are hives. Non-allergy-related rashes may be flat, blotchy, and spread over days rather than hours. Since it may be difficult to tell the difference, and you can't always get to a doctor right away, take a photograph of the rash to help with the diagnosis.
Avoiding penicillin if there isn't an allergy diagnosis is not the best idea.
Alternative antibiotics to penicillin - often called "broad-spectrum" - may be less effective in treating your infection, may cause unwanted side effects or may be more expensive. Don't limit your treatment choices - find out for sure whether you are allergic.
Testing for penicillin allergy is safe and reliable.
The process is simple. First, the patient undergoes a series of skin prick tests, using gradually increasing amounts of penicillin. A raised wheal at the site of the prick indicates allergy. If the tests are negative, the next step is an oral challenge - drinking liquid penicillin. These tests should always be conducted by an allergist trained to recognize and treat potential allergic reactions.

Side Effects of Penicillin Antibiotics Can Include

abdominal pain
allergic reactions
black or hairy tongue
bleeding
confusion
diarrhea
dizziness
easy bruising
heartburn
insomnia
itching
nausea
rash
stomach cramps
vomiting

Serious but Rare Penicillin Reactions Can Include:

kidney problems
low blood platelet levels (thrombocytopenia) or red blood cell count
oral fungal infections
seizures
severe allergic reactions (anaphylaxis)

Reactions to penicillin may vary - including many additional symptoms not mentioned above - between different strains or types administered.

"Anyone who believes they are allergic to penicillin because they had a reaction years ago should undergo testing with a board-certified allergist," says Courtney Blair, MD, board-certified allergist in McLean, Virginia and Anaphylaxis Community Experts (ACE) volunteer with Allergy & Asthma Network. "If you are found to be allergic, then you'll have a confirmed diagnosis and will know what to avoid. If you're not, then you'll know that if you need penicillin, you can take it without concern."

When you're facing a medical treatment, you want the best possible care. Why limit your treatment to less effective drugs, or those with potentially more serious side effects? Talk with your physician about your past reactions with penicillin, and see a board-certified allergist to determine if testing is warranted.

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