What Is a Penicillin Allergy?
Penicillin is one of the most popular antibiotic drugs in the world. It was discovered in 1928 by scientist Alexander Fleming. Doctors began widely using this drug in 1942 to treat bacterial infections.
Today, penicillin is one of many antibiotics used for bacterial infections. It is commonly used to treat strep throat and skin infections. Penicillin works by damaging the outer wall of bacteria, causing the bacteria to die.
Some people are worried about taking penicillin because they’ve been told in the past they had an allergic reaction. They may fear they will develop an allergic reaction as a result. About 10% of people in the US believe they have a penicillin allergy, but fewer than 10% of those people actually do. About 80% to 90% of people who were once allergic to penicillin lose their allergy after 10 years.
It is important to know for certain whether you are allergic to penicillin. If you are not, but your medical history says you are, you could be given less effective or less appropriate antibiotics. Testing performed by a board-certified allergist is the most reliable way to confirm whether you have a true penicillin allergy.
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Common Penicillin Antibiotics
Doctors prescribe penicillin in different forms, including pills, liquids, and injections. Penicillin may be prescribed under different names. Here is a list of some penicillin-containing drugs:
- Penicillin
- Ampicillin
- Amoxicillin
- Amoxicillin-clavulanate
Are You Allergic to Penicillin?
You probably know someone who says they have a penicillin allergy. Or perhaps you think you are penicillin allergic. Maybe you have taken this drug in the past and developed a skin rash. Or maybe you’ve never taken penicillin but you’re wondering how your body might react to it. In either case, you should see an allergist to be tested.
Allergists collect your medical history, perform tests, and offer treatment options.
Penicillin Allergy Symptoms
If you have a true penicillin allergy, your immune system might develop antibodies – proteins your body makes to fight germs. This can cause mild to severe allergy symptoms, including:
- Hives or a skin rash
- Itching
- Wheezing or breathing problems
- Swelling
- Vomiting
- Feeling dizzy or lightheaded
- Anaphylaxis, a severe reaction that is life-threatening and needs to be treated immediately
Anaphylaxis can impair breathing and can affect more than one organ. For example, you may develop a rash (skin) and breathing problems (lungs).
Anaphylaxis symptoms include:
- Trouble breathing
- Wheezing
- Swelling of the throat, tongue, or lips
- Tight chest
- Dizziness or fainting
If anaphylaxis develops and you’ve been prescribed epinephrine, use your epinephrine immediately. If your severe symptoms don’t resolve after a second dose of epinephrine, call 911 and seek emergency medical care.
Penicillin Allergy Treatment
Your allergist will determine the best treatment for avoiding penicillin allergy reactions. If you have a mild reaction to penicillin, treatment might include taking an antihistamine like cetirizine or diphenhydramine to reduce hives or itching. Some antihistamines start to work within 15 to 60 minutes.
A steroid medicine taken by mouth may be another treatment for a mild penicillin allergy. Prednisone is an example of a steroid. It works by reducing swelling in the body. This calms down the immune system’s response in the body.
People who have severe reactions to penicillin, including swelling of the throat, tongue, or lips, or difficulty breathing, need to be treated immediately with epinephrine, the first-line treatment for severe allergic reactions.
Epinephrine can be carried with you and used in any situation where anaphylaxis might occur. If you have a prescription for epinephrine, it’s best to always carry two doses with you.
Penicillin Allergy Diagnosis
A physical exam, skin test, and an oral challenge help allergists determine if you have a true penicillin allergy. If you are having symptoms, your allergist may ask you questions, like:
- What is the name of the drug you are taking?
- Why were you prescribed this drug?
- How long ago did the reaction occur?
- What other medications are you taking?
- Can you describe your symptoms?
You can help your doctor diagnose if you have a penicillin allergy by sharing information about your current symptoms and remembering past symptoms you had when taking penicillin.
Note: If it turns out you are not allergic to penicillin, it’s important to alert your primary care physician, as well as any other health care providers you see regularly. You should also let your pharmacist know, as they may have penicillin allergy in your chart, and may need to see information from your allergist.
Skin Test for Penicillin Allergy
The skin test is not painful. Here’s how it works:
A small amount of penicillin is placed under your skin with a tiny needle. If your skin develops an itchy bump, that means you tested positive for penicillin allergy. If nothing happens, you’re considered negative for penicillin allergy, but more tests may be needed to confirm.
Oral Challenge
The allergist will give you a controlled dose of penicillin and observe your body’s reaction to it. This takes place in a medical setting with rescue medication available.
Graded Challenge
Sometimes you might have a graded challenge, which is another step in knowing if you are truly allergic to penicillin. With this procedure, you could receive increasing doses of penicillin to see your reaction. This helps your allergist find the safest type and amount of penicillin for your body.
Management
People who test positive on allergy skin tests should avoid penicillin and be treated with a different antibiotic. If penicillin is the best option for your infection, your doctor might help you to desensitize your body so that you can safely take it.
Here are several things you can do to protect yourself if you are allergic to penicillin:
- Tell all your doctors and your pharmacist about your penicillin allergy. Also let your doctors and pharmacists know if a previously diagnosed penicillin allergy is no longer present.
- Carry an epinephrine device if prescribed.
- If you have a severe penicillin allergy, wear a medical alert bracelet.
- Ask for antibiotics that do not contain penicillin.
FAQs
Symptoms can happen within an hour but can also happen days later.
Most antibiotic drugs with “cillin” in the name are part of the penicillin family. Always check with your pharmacist to be sure. You should not rely on the name of the drug to know if it contains penicillin.
A skin reaction is the most common penicillin allergy symptom. This can show up as a rash, hives (raised itchy patches), or itching.
Azithromycin, clarithromycin, doxycycline, and clindamycin. If you have a penicillin allergy, your doctor will decide which antibiotic to give you based on your illness.
Not necessarily. Between 80% to 90% of patients who have a penicillin allergy tend to lose it a decade later. It’s important to be tested by a board-certified allergist to know if you’re still allergic.
