What Penicillin Is and Where It’s Found
Penicillin medications are a type of antibiotic formulated from Penicillium fungus. A funny meme making its rounds on the Internet says, “When life gives you mold, make penicillin.”
It’s true that the fungus used in penicillin was discovered by accident when staph bacteria being used in an experiment was contaminated with mold. When the mold killed off the staph bacteria, an antibiotic was discovered!
Penicillin today is typically made synthetically, but it works the same way. There are many penicillin antibiotics, including some you’re likely familiar with—such as amoxicillin, a commonly prescribed antibiotic for infections such as strep.
Recognizing the Signs of a Penicillin Allergy
When your doctor gives you a prescription, even if it’s not for the first time, keep an eye on your overall health. Report any changes you feel after taking a medication to your doctor or pharmacist.
That’s particularly important when you’re taking an antibiotic to treat an infection. While drug allergies are relatively rare, antibiotics are among the most common sources of drug allergies.
If you have an allergy to penicillin, you may feel:
- Chest tightness
- Fainting
- Hives
- Joint pain
- Shortness of breath
- Skin redness
- Swelling of the abdomen, face, extremities or throat
- Wheezing
Symptoms such as shortness of breath, chest tightness, wheezing or throat swelling can all be related to anaphylaxis, a potentially life-threatening allergic reaction. People who experience any of these symptoms should seek immediate medical attention. Report less serious symptoms to your doctor’s office.
How to Determine Whether You’re Allergic to Penicillin
Penicillin can cause other effects, such as fatigue or upset stomach. These are not considered allergic reactions. They’re side effects of the medication itself.
Allergy testing can tell the difference between a side effect or a penicillin allergy. Your primary care doctor can refer you to an allergy specialist for testing.
Penicillin allergies can be confirmed using either a skin test or an oral challenge. Skin testing is a common test that involves pricking the skin with two types of penicillin. If a person is allergic to penicillin, you’ll see a raised red bump at the site of the skin prick.
In some cases, an oral penicillin challenge will follow the skin test or be used as a standalone test. Your allergist will give you a small dose of amoxicillin and watch for an allergic reaction.
Why is it important to confirm if you’re allergic to penicillin? If your doctor has reason to believe you have an allergy, you may need to avoid penicillin and other related medications, such the cephalosporin class of antibiotics. Allergies substantially limit the antibiotics you can take, a potential health issue if you’re unable to take other antibiotics or develop resistance to them.
If you know for sure that you have a true penicillin allergy, your doctor can safely prescribe antibiotics when you get a bacterial infection in the future.
If you have an allergy to penicillin, there’s good news. As many as 80 percent of those with a penicillin allergy are no longer allergic after 10 years. You may get different results when you are reevaluated for a penicillin allergy later in life.
More to Read
- Allergic Reactions: Why Reacting Quickly Saves Lives
- How to Know if You’re Having an Allergic Reaction to Antibiotics
- Should I Go to the ER, Urgent Care or Primary Care?
- Should I Take My Child to the Emergency Room?
Medically reviewed by Carolyn Ridenour Helmly, MD.
