Am I Allergic to Penicillin?


Florida Medical Clinic Allergy, Asthma & Immunology

Despite 10% of the American population believing they are allergic to penicillin, allergy testing rules out 90% of these cases. According to the U.S. Centers for Disease Control and Prevention, only 1% of people actually have a penicillin allergy. Furthermore, 80% of people diagnosed with the allergy lose their sensitivity to the drug after 10 years.

Penicillin is the name for a group of antibiotics used to treat bacterial infections, including strep throat and ear, sinus and respiratory infections. They are very effective in treating a narrow range of harmful bacteria and have a low toxicity. The penicillin family is part of a larger class of beta-lactam drugs, so people who report being allergic to penicillin miss the benefits of a large number of medicines. Doctors are reluctant to prescribe beta-lactam antibiotics for fear of an allergic reaction.

Being labeled with a penicillin allergy can be detrimental to a patient’s health. It’s associated with increased hospital length of stay, increased perioperative infections, and overall increased mortality. A patient might be prescribed broad-spectrum antibiotics that are not as effective, have more side effects and toxicities, and kill good bacteria that help our bodies function. These drugs might be more expensive and take longer to work. In addition, the use of broad-spectrum antibiotics contributes to the development of drug-resistant bacteria.

For these reasons, as well as the possibility of suffering an allergic reaction to penicillin, it’s important to know where you stand. In this article, we’ll cover:

  • Allergic symptoms and severe reactions
  • Common symptoms of a penicillin allergy
  • Life-threatening conditions
  • Side effects
  • How to get a penicillin allergy evaluation
  • Penicillin skin testing
  • Challenge doses
  • Understanding a positive skin test

Allergic Symptoms and Severe Reactions

Penicillin allergic reactions occur when the body’s immune system responds to the antibiotic as if it were a harmful substance. Some people have sudden, severe signs and symptoms. Others have milder reactions that take longer to develop.

Common symptoms of a penicillin allergy

People with a penicillin allergy may experience an immediate onset of symptoms, like a skin rash. Allergic reactions can occur within seconds of taking the drug or up to several days later. Children sometimes experience reactions a week after receiving penicillin. These reactions may include joint pain, fever, hives, and joint stiffness.

Symptoms of a penicillin allergy range from mild to extremely severe:

    • Skin reaction
    • Throat tightness
    • Chest tightness
    • Joint pain
    • Coughing
    • Nasal congestion
    • Swelling in your hands, feet, and face
    • Rapid heartbeat
    • Dizziness
    • Anaphylaxis, a life-threatening reaction that must be treated as a medical emergency

Symptoms such as a red, itchy, rashy, or swollen face may indicate an allergy to penicillin. However, there are other possible causes for these reactions. Viral infections, side effects of antibiotics, and secondary infections are all conditions that could be mistaken for penicillin allergies.

Life-threatening allergic reactions

Some reactions to a penicillin allergy are life threatening. Anaphylaxis is one of the most severe allergic responses. Symptoms of anaphylaxis include respiratory distress, wheezing, dizziness, low blood pressure, and chest tightness. Anaphylactic shock may cause a person to stop breathing or stop the heart from beating. Anaphylaxis requires immediate treatment, typically including an epinephrine injection.

A rare, severe reaction called toxic epidermal necrolysis (TEN) causes peeling of the skin and mucous membranes. If left untreated, it can lead to sepsis and death.

Side effects

Many medicines have side effects, which differ from allergic reactions. Most adverse effects are mild in comparison to an allergic reaction. Still, the symptoms can be quite similar, such as a rash and itching skin. Mild, transient side effects are the norm and generally disappear within a few days. The most common side effects experienced after taking penicillin are:

  • Weakness
  • Nausea
  • Vomiting
  • Headache
  • Skin itchiness at the injection site

For comparison, let’s recap some common penicillin allergy symptoms:

  • Severe skin rash
  • Extreme nausea and vomiting
  • Diarrhea
  • Difficulty breathing
  • Tightness in the chest
  • Swelling in your hands, feet, or face

Always seek medical treatment if you notice any of the symptoms listed above after taking penicillin.

How to Get a Penicillin Allergy Evaluation

Anyone can develop an allergy to penicillin at any time. An allergist or immunologist can run tests to make a determination.

Penicillin skin testing

Diagnosis includes gathering the patient’s complete medical history, doing a physical examination, and possibly conducting skin testing, such as the scratch test and the intradermal test.

The scratch test involves placing two drops of penicillin on the skin. The doctor then makes a small scratch or a skin prick through each drop. After about 15 minutes, the doctor will look for redness, itching, and hives on the skin to confirm a positive diagnosis.

The intradermal test involves injecting a very small amount of penicillin beneath the skin with a thin needle. If a small bump arises at the injection site, it confirms a positive diagnosis of a penicillin allergy.

Challenge doses

If the skin testing is negative, or if doctors don’t think it’s necessary, they may proceed with an oral challenge. They may administer a test dose and look for a reaction, the continue in steps up to a full dose. The combination of skin testing and challenge doses is nearly 100% accurate in ruling out a penicillin allergy.

Understanding a Positive Skin Test

The best time to find out whether you have a penicillin allergy is before you have a negative reaction. Being aware of the allergy allows doctors to provide you with better care. If you have a positive allergy test, be sure to notify all your healthcare providers. This includes your regular care providers, like your family doctor and dentist, as well as any specialists you may see. Patients who have severe reactions might be advised to wear medical alert bracelets to alert others in an emergency.

If a doctor decides that a drug from the penicillin family is essential for treatment of an illness, they may recommend drug desensitization. This process builds a temporary tolerance for the drug. A doctor carefully monitors the patient while building from a miniscule dose of penicillin to larger doses, ending with a full therapeutic dose. The process may take several hours.

Drug desensitization doesn’t permanently take away the allergy. A patient may need additional desensitization if penicillin is required again.

Getting the Answers You Need

At the Florida Medical Clinic, our team of highly trained specialists can help you with any concerns you have regarding allergies. The immunology department helps with all types of penicillin allergy testing, diagnosis, and treatment.

About Sami Nallamshetty, MD, FACAAI

Dr. Sami Nallamshetty specializes in pediatric and adult allergy and immunology at Florida Medical Clinic locations in Brandon, Carrollwood and Wiregrass. Her studies on allergies and asthma were published in top scientific journals. She was also recognized by her peers and Tampa Magazine as a Top Doctor in Allergy, Asthma & Immunology in 2022, 2021 and 2016.

Dr. Nallamshetty calls on her extensive education, Fellowship, and experience to overcome her patients’ medical problems. Her passion for patient care has helped many patients alleviate their illnesses and allergies. If you suffer from allergy & asthma symptoms, schedule an appointment with Dr. Nallamshetty.


Meet Daniel A. Reichmuth, MD, FAAAAI, FACAAI

Dr. Daniel Reichmuth is an award-winning allergist-immunologist who practices at Florida Medical Clinic’s locations in Land O’Lakes, Wiregrass, and WaterGrass.

A graduate of the Indiana University School of Medicine, Dr. Reichmuth has published several medical articles and is trusted to educate other professionals in his field.

Dr. Reichmuth specializes in allergic rhinitis, sinus disease, asthma, eczema, hives, cough and all types of allergies and allergy testing.  Schedule an appointment with Dr. Reichmuth today to address your allergy or asthma symptoms.


Allergy, Asthma & Immunology

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