What Is Penicillin Allergy?

Penicillin is an antibiotic medication for treating bacterial infections. Since its mid-20th century introduction, penicillin has become one of the most common and effective means of combating a variety of disease pathogens. A penicillin allergy occurs in persons whose immune systems are unusually sensitive to the drug, leading to an adverse physical reaction. Penicillin allergies affect a relatively small portion of the population and sometimes diminish over time.

Allergic reactions to penicillin differ in severity. Mild cases are marked by hives, itchiness, and swelling, while more serious cases can result in anaphylaxis and are therefore life-threatening. If you or a loved one experiences an allergic reaction to penicillin, contact your prescribing physician, call 911, or go to the nearest emergency medical facility for treatment.

What Are Common Types of Penicillin?

Penicillins are beta-lactam antibiotics developed originally from bacteria-killing molds. Several types of penicillin are in use today as both oral and injectable medications. Included among these are:

• Amoxicillin
• Ampicillin
• Dicloxacillin
• Nafcillin
• Oxacillin
• Penicillin G
• Penicillin V

Some earlier forms of penicillin, including carbenicillin and ticarcillin, are no longer in use.

Symptoms of Penicillin Allergy

Common Symptoms of Penicillin Allergy

Penicillin allergies are marked by a wide range of potential symptoms. Reactions typically begin within an hour or two of taking penicillin. The most common symptoms include:

• Coughing
• Fever
• Hives
• Itchiness
• Runny nose
• Swelling (angioedema)
• Watery eyes
• Wheezing

Immunological reactions such as these are distinguished from the more common adverse reactions that many people experience with drugs. Adverse reactions to penicillin are usually mild and include upset stomach, headaches, fatigue, and vaginal itching. These are non-immunological responses that do not imply the existence of an allergy.

Severe Symptoms

More serious reactions occur in some cases. The following symptoms, typical of anaphylaxis, are potentially life-threatening:

• Cramping
• Diarrhea
• Drops in blood pressure
• Elevated heart rate (tachycardia)
• Labored breathing
• Lightheadedness
• Loss of consciousness
• Nausea
• Seizures
• Vomiting

In addition to these symptoms, penicillin allergies have been linked to certain kinds of delayed reactions, such as serum sickness, kidney inflammation, anemia, and Stevens-Johnson syndrome, a severe flaking and blistering of the skin.

When to See a Doctor

See your physician if you’ve taken penicillin and develop evidence of an allergic reaction. This is especially important if you experience unusual or potentially life-threatening symptoms, such as difficulty breathing, rapid heartbeat, lightheadedness, cramping, and diarrhea. In the most serious cases, call 911 or seek care at a nearby emergency medical facility.

Causes and Risk Factors of Penicillin Allergy

Causes of Penicillin Allergy

A penicillin allergy is the result of a person’s immunological system responding negatively to the presence of penicillin in the body. In essence, the immune system begins fighting the very medicine a person has taken to combat another infection already present. The reasons for this immunological sensitivity are unknown. Allergies can appear suddenly but also fade over time, which seems to be true for many individuals reporting a penicillin allergy.

Risk Factors

Certain medical conditions may increase your likelihood of developing an allergic response to penicillin. These include:

• Asthma
• Eczema
• Hay fever

Your risk of a penicillin allergy may also be greater if you have previously experienced an immunological reaction to a non-penicillin drug.

Diagnosis of Penicillin Allergy

Diagnosing a penicillin allergy requires a physician. He or she will take the following steps to determine whether you experienced an immunological reaction to penicillin:

• Conduct a physical exam: Your physician will check your vitals and look for physical signs of an adverse reaction to penicillin. He or she will ask you questions about your medical episode and will also look for possible risk factors in your medical history.
• Perform a skin-prick test: A nurse or medical technician will use a needle to introduce trace amounts of penicillin to the surface of your skin. If a positive reaction occurs – meaning a small, red, itchy bump develops – it may indicate a penicillin allergy.
• Perform an intradermal test: This test is like the skin test, but the penicillin is introduced below the dermal surface. Your physician will be looking for a similar positive reaction. An intradermal test can help confirm the results of the skin-prick test.
• Conduct a graded challenge: The graded challenge is typically performed to corroborate the negative results of the two skin tests. You take a small dose or doses of penicillin under medical supervision. A negative or non-reaction to penicillin during a graded challenge indicates a lack of allergy.

Managing and Treating Penicillin Allergy

Immediate Treatment of Allergic Reactions

The treatment of a penicillin allergy typically involves the following steps:

• Immediate disuse of penicillin
• Taking a prescribed corticosteroid, such as cortisone or prednisone, to reduce itching and swelling
• Taking an antihistamine, such as loratadine or cetirizine, to control allergy symptoms

Epinephrine is required to counteract anaphylaxis in emergency situations. This can be self-administered by means of a portable injector or obtained in an emergency medical facility.

Long-term Treatment and Alternatives

There are alternative antibiotics for treating bacterial infections for persons with a penicillin allergy. Among these drugs are:

• Ciprofloxacin
• Clarithromycin
• Doxycycline
• Gentamicin

These are broad-spectrum antibiotics that target large classes of bacteria. They can be effective substitutes for penicillin but are also playing a role in the development of new strains of drug-resistant bacteria. A second alternative for persons with a penicillin allergy is drug desensitization. You may be able to desensitize your immune system to the presence of penicillin through a program of introducing progressively larger amounts of penicillin over an extended period. If you can tolerate a full dosage of penicillin delivered gradually, you may be able to use the drug in the future to combat infection.

Preventing Penicillin Allergic Reactions

If you’re allergic to penicillin, you can avoid an allergic reaction simply by not taking the drug. Be sure to tell any medical provider you see in the future about your allergy. If you’ve never taken penicillin or haven’t had it in a long time, you can’t be certain about an allergy. Consider being tested by your physician.

Why Choose Baptist Health for Allergy Care?

A penicillin allergy is a negative immunological reaction to penicillin. It can result in a variety of symptoms, ranging from rashes, swelling, itchiness, runny nose, and watery eyes to more serious responses, including shortness of breath, low blood pressure, elevated heart rate, and seizures. These latter symptoms, typical of anaphylaxis, are potentially life-threatening. Baptist Health is committed to being a leading provider for allergy diagnosis and treatment in Kentucky and Southern Indiana. If you have questions or concerns about an allergy, contact your Baptist Health primary care physician or one of our specialists.

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FAQs About Penicillin Allergy

Is Penicillin Allergy Hereditary?

Penicillin allergies are not directly hereditary. If a parent has a penicillin allergy, it won’t automatically pass to you, nor must you avoid penicillin unless you show evidence of developing the allergy.

How Long Does an Allergic Reaction to Penicillin Last?

A penicillin reaction can last two to four weeks. The variation in length of time is caused by differences in body chemistry between peoples.

Can I Take Amoxicillin If I’m Allergic to Penicillin?

No. Amoxicillin is chemically related to penicillin and is likely to cause a similar type of allergic reaction.

Can I Take Benadryl If I’m Allergic to Penicillin?

Yes. Benadryl is an antihistamine rather than an antibiotic and can be taken to reduce hives or itching.

Can I Take Zyrtec If I’m Allergic to Penicillin?

Yes. Zyrtec is an antihistamine rather than an antibiotic and can be taken to reduce hives or itching.