Penicillin Allergy: Causes, Symptoms, Diagnosis and Treatment

A penicillin allergy is an abnormal reaction of your immune system to the antibiotic penicillin. Penicillin is prescribed to treat various bacterial infections.

Common signs and symptoms of penicillin allergy include hives, rashes, and itching. One of the serious reactions is anaphylaxis, a life-threatening condition that affects multiple body systems.

Research has shown that penicillin allergies have been overdiagnosed, a problem that can lead to the use of less appropriate and more expensive antibiotic treatments. Therefore, an accurate diagnosis is necessary when a penicillin allergy is suspected to ensure the best treatment options.

Other antibiotics, especially those with similar chemical properties to penicillin, can also cause allergic reactions.

Signs and symptoms of a penicillin allergy often appear within an hour of taking the drug. Less commonly, reactions can occur hours, days or weeks later.

Here are some of the signs and symptoms of a penicillin allergy: Rash Hives Itchy Fever Swelling Shortness of breath Wheezing Catarrh Itchy, watery eyes Anaphylaxis

Anaphylaxis is a rare, life-threatening allergic reaction that causes generalized dysfunction of body systems. Signs and symptoms of anaphylaxis include: Narrowing of the airways and throat, causing difficulty breathing Nausea and cramps Vomiting or diarrhea Dizziness or vertigo Weak and rapid pulse Drop in blood pressure Seizures Unconsciousness

Less common allergic reactions to penicillin occur days or weeks after exposure to the drug and may persist for some time after treatment is stopped. These disorders include the following:

serum sickness, which can cause fever, joint pain, rash, swelling, and nausea

drug anemia, a reduction in red blood cells, which can cause fatigue, irregular heartbeats, shortness of breath, and other signs and symptoms

Drug reaction with eosinophilia and systemic symptoms (DRESS), causing rash, high white blood cell count, general swelling, swollen lymph nodes, and recurrence of latent hepatitis

Stevens-Johnson syndrome or toxic epidermal necrolysis, involving severe blistering and peeling of the skin

Inflammation of the kidneys (nephritis), which can cause fever, blood in the urine, general swelling, confusion, and other signs and symptoms

You may have side effects from penicillin (as you do with other drugs) that are not an allergic reaction to the drug. Depending on the type of penicillin, the most common side effects are mild headache, vaginal itching, nausea or diarrhea. Signs or symptoms of an infection for which you are being treated (or unrelated symptoms) can also be mistaken for an allergic reaction to the drug.

See your doctor as soon as possible if you have any signs or symptoms of penicillin allergy. It is important to understand and discuss what an allergic reaction is, what a typical side effect is, and what you can tolerate while taking medication.

Call 911 or an emergency care service if you have signs of a severe reaction or suspect anaphylaxis after taking penicillin.

Although anyone can have an allergic reaction to penicillin, certain factors can increase this risk. These include:

History of other allergies, such as food allergy or hay fever Allergic reaction to another drug Family history of drug allergy Increased exposure to penicillin, due to high doses, repetitive use, or prolonged use Certain conditions commonly associated with allergic reactions to drugs, such as HIV infection or Epstein Barr virus

A complete examination and appropriate diagnostic tests are essential for an accurate diagnosis. A misdiagnosed penicillin allergy can lead to the use of less appropriate or more expensive antibiotics.

The doctor will perform a physical exam, ask about symptoms, and order additional tests. You may be referred to an allergy specialist (allergist) for these tests. These may include the following:

With a skin test, your allergist or nurse administers a small amount of the suspected penicillin to your skin with a small needle. A positive reaction to a test will cause a red, itchy, raised bump.

A positive result indicates a high probability of penicillin allergy. A negative result usually means you are not at high risk for penicillin allergy. But a negative result is more difficult to interpret because some types of drug reactions cannot be detected by skin testing.

If the diagnosis of penicillin allergy is uncertain, enhanced drug challenge may be recommended. In this procedure, up to five doses of penicillin are administered; start with a small dose until you reach the desired dose. If you reach the therapeutic dose without a reaction, your doctor will conclude that you are not allergic to this type of penicillin. You can take the drugs according to the medical indications.

If you are allergic to a type of penicillin, your doctor may recommend a staged challenge test with a type of penicillin or with a cephalosporin that is less likely to cause an allergic reaction (due to known chemical properties). Thus, the doctor could identify which antibiotic can be used safely.

During a challenge test, the doctor monitors closely and supportive care services are provided to treat an adverse reaction.

Interventions to treat penicillin allergy can be divided into two general strategies:

Treatment of existing allergic symptoms Penicillin desensitization

To treat the symptoms of an allergic reaction to penicillin, the following procedures can be performed:

Stop the medicine. If your doctor determines that you have a penicillin allergy, or a possible allergy, the first step in treatment is to stop the medication.

Antihistamines. Your doctor may prescribe an antihistamine or recommend an over-the-counter one, such as diphenhydramine (Benadryl), which blocks immune system chemicals activated during an allergic reaction.

Corticosteroids. Oral or injectable corticosteroids can be used to treat inflammation associated with the most severe reactions.

Treatment of anaphylaxis. Anaphylaxis requires an injection of epinephrine and immediate hospital care to maintain blood pressure and support breathing.

If no other suitable antibiotic treatment options are available, your doctor may recommend a treatment called drug desensitization, which may allow you to take penicillin therapy to treat an infection. With this treatment, you receive a very small dose and then gradually larger doses every 15 to 30 minutes for several hours or a few days. If you can reach the desired dose without reaction, you can continue treatment.

It is important that you take the medicine as directed to maintain your tolerance throughout treatment. If you need penicillin in the future, you will need to repeat the desensitization treatment.

You are carefully monitored during the procedure and supportive care is available to deal with reactions. Desensitization is not always successful and there is a risk of serious reactions.