Penicillin Allergy: Types, Symptoms, Treatment, Diagnosis and Prevention

An allergic reaction to penicillin drug is known as penicillin allergy. It leads to hives, shortness of breath, and areas of swelling. In some cases, penicillin allergy may cause anaphylaxis, a life-threatening condition that causes low blood pressure, feeling of faintness, and rapid heartbeat.

A person can develop an allergy if the immune cell produces antibody IgE on being exposed to penicillin or similar antibiotics. Penicillin on being attached to IgE antibodies releases histamine that causes symptoms of allergy such as itching and hives.

Other Types of Penicillin Allergy Are:

• Cytotoxic Drug Allergy: In this, there are serious drug reactions such as thrombocytopenia, and low platelet count in the blood.
• Immune Complex Delayed Hypersensitivity: It includes fever, rash, hives, swelling, and joint stiffness.
• Immunological Nephropathy: It involves a kidney disorder.

According to the American Academy of Allergy, Asthma and Immunology, about 10% of the population report penicillin allergy among them 90% have negative allergy testing which means they can take penicillin without allergic symptoms. ⁽¹⁾

This means most people with a diagnosis do not have allergies.

Repeated and frequent penicillin doses can be a major risk factor for an IgE allergic reaction. ⁽³⁾ Also, receiving high doses of medication via injection can also be a risk factor for penicillin allergy.

If a person is allergic to penicillin, on taking penicillin immunoglobins may be triggered and symptoms appear immediately. ⁽²⁾ The symptoms include:

• Hives, which are inflamed, itchy raised areas on the skin
• Angioedema, which are localized areas of swelling without hives affecting the face, abdomen, genital, throat, arms, or legs
• Shortness of breath and wheezing
• Anaphylaxis

Some people also experience a delayed type of allergic reaction that causes an itchy rash that might not appear until several days after starting penicillin antibiotics. This condition is known as a maculopapular rash.

A type of penicillin allergy may lead to a serum sickness type of reaction. This rash occurs with fever and fatigue along with other symptoms.

Anaphylaxis is a life-threatening condition in which the symptoms occur immediately or an hour after taking penicillin. The symptoms that are commonly seen occurring in an anaphylactic reaction include:

• It involves hives, flushing, angioedema, or itching
• There may be coughing, shortness of breath, tightness, nasal congestion, the sensation of choking, wheezing, or throat closure
• Nausea, vomiting, diarrhea, and pain are also symptoms of an anaphylactic reaction.
• There may be a rapid heartbeat, low blood pressure, and fainting feeling.

Delayed reactions occur days to weeks after taking penicillin. ⁽⁴⁾ The symptoms include:

• Toxic epidermal necrolysis, a life-threatening reaction
• Hemolytic anemia is a condition in which the red blood cells get destroyed faster than being replaced.
• Steven Johnson Syndrome, a serious reaction to medication that affects the mucous membranes.
• Serum sickness, a disorder similar to an allergy
• Vasculitis or the inflammation of blood vessels
• Interstitial nephritis, a kidney disorder
• Thrombocytopenia, a condition in which there is bleeding bruising, or slow blood clotting after an injury
• Neutropenia, having too less white blood cells

Diagnosing penicillin allergy starts with taking a medical history and examining the patient. The doctor enquires about the previous abnormal reactions to penicillin.

A skin test known as penicillin skin test is done. In a positive reaction, a raised inflamed area, at least 3 mm wide occurs on the skin in 15 minutes. ⁽³⁾

If the prick test is negative and still penicillin allergy is suspected, an intradermal test may be conducted. In this, a small amount of penicillin is injected a little deeper between the skin layers. Just like the skin prick test, in this too there is a raised skin area of 3mm wide.

The skin prick test and intradermal test can be useful only for IgE-mediated penicillin allergy. It cannot be helpful in diagnosing other types of penicillin allergy.

The treatment of penicillin allergy depends on the severity of the allergic reaction.

Antihistamines may be prescribed for even mild rashes and itching.

In anaphylaxis reaction antihistamines, glucocorticoids, and bronchodilators are given. Glucocorticoids help in relieving inflammation and bronchodilators dilate airways. Some symptoms of anaphylaxis may need medical attention. These symptoms include blistering and peeling of the skin accompanied by fever and fatigue.

In case of allergy to penicillin, other alternatives to penicillin can be used.

If no other treatment is effective besides penicillin for a particular illness, desensitization can be an option.

In this process, a person is given incrementally higher doses of penicillin until he is able to tolerate the entire usual dose. It can give doses orally or by injection.

It is important to see a doctor as soon as possible for any signs and symptoms of allergic reaction to avoid complications.