Penicillin Allergy – Causes, Signs and symptoms

Penicillin Allergy


Penicillin allergy is one of the most common kinds of drug allergies. It occurs when the immune system reacts to the presence of the drug penicillin or a related form such as amoxicillin or ampicillin. Symptoms of a penicillin allergy include a rash, hives, itchy eyes and swollen lips, tongue or face (angioedema). People who believe they are having an allergic reaction to penicillin should immediately contact a physician.

In highly susceptible individuals, a penicillin allergy can also result in a potentially life threatening condition known as anaphylactic shock. This condition is characterized by difficulty breathing and lowered blood pressure. Anyone who experiences severe reactions after taking penicillin should contact 911 immediately.

A physician can use a skin test or a RAST test to safely determine whether a person is allergic to penicillin and, if so, how sensitive they are. Penicillin allergies tend to be somewhat more common in children than adults, especially in those under the age of 10. Furthermore, children frequently lose this sensitivity over a period of years. However, the danger of a penicillin allergy is such that once even a mild reaction occurs, patients are usually directed to avoid the drug for the rest of their lives.

The most effective way to treat a penicillin allergy is to completely avoid the drug type (and related drug types in some cases). This can be accomplished by working closely with a physician to ensure that alternate forms of antibiotics are used when penicillin normally would. Individuals who are highly sensitive to penicillin should wear a medical alert bracelet or necklace to inform healthcare workers of their condition in the event of an emergency.

For those individuals who do experience symptoms from a penicillin allergy, several types of drugs are available to treat the condition. Antihistamines, bronchodilators and corticosteroids can all provide relief from allergy symptoms. Epinephrine is used to treat anaphylactic shock, and physicians often recommend that highly sensitive individuals carry a shot of epinephrine with them at all times.

About penicillin allergy

Penicillin and other antibiotics are the most common source of drug allergies. Penicillin belongs to a family of antibiotic drugs known as beta–lactam antibiotics. Individuals who are allergic to one type of penicillin are usually allergic to them all (e.g., amoxicillin, ampicillin). Additionally, some people may also be allergic to the family of antibiotics known as cephalosporins (e.g., cefazolin, cephalexin), which are chemically similar to penicillins.

Penicillins are normally used to treat:

  • Infectious diseases (e.g., pneumonia, tuberculosis)
  • Infections of the ears, nose and throat
  • Respiratory and urinary tract infections
  • Prostate infections
  • Sexually transmitted diseases

An allergic reaction to penicillin occurs when the drug enters the body, usually orally (a pill or liquid), intravenously (an injection) or intramuscularly (injection into a muscle). A reaction is triggered when the immune system overreacts to the penicillin, mistaking it for a dangerous substance. To combat the drug, the immune system releases IgE antibodies into the bloodstream. These antibodies interact with mast cells and basophils, and trigger these to release histamines and other chemicals.

It is the histamines and other chemicals that stimulate allergy symptoms. By causing blood vessels to swell and individual cells to leak fluid, histamines produce allergy symptoms such as itchiness, rash, hives, stomach cramps, nausea and respiratory problems. Individuals who are highly susceptible to allergic penicillin reactions can go into life–threatening anaphylactic shock, which involves difficulty breathing and lowered blood pressure.

People who suspect that they are having an allergic reaction to penicillin should immediately contact a physician. If the reaction is severe, a person should promptly contact 911 for medical help. 

The U.S. Department of Health and Human Services estimates that over 400 Americans are killed each year from anaphylactic reactions to penicillin.

It is unknown why some individuals develop penicillin allergies, while others do not. However, some experts believe heredity may be a factor.

People with allergies to penicillin generally find their reactions decrease over time. The American Academy of Allergy, Asthma and Immunology estimates that only 20 percent of individuals who have an allergic reaction to penicillin are susceptible to penicillin 10 years later (provided there is no exposure during that time period). However, individuals who have an allergic reaction to penicillin are generally advised to never use the medication again for precautionary reasons. Physicians can usually use a different form of antibiotic to treat any problems.

Potential causes of penicillin allergy

Penicillin is part of a family of drugs known as beta–lactam antibiotics. An allergy to one form of penicillin means that every drug in the beta–lactam family can be dangerous. Other types of penicillin are used to combat different types of infections in various parts of the body. The several types of penicillin an allergic individual must be careful to avoid include:

  • Amoxicillin. The most commonly used type of beta–lactam, this drug is often used in the treatment of strep throat and ear infections.

  • Ampicillin. Able to penetrate and prevent the growth of various forms of bacteria. It is often used to treat infections of the middle ear, sinuses, bladder and kidney.

  • Dicloxacillin. Used to treat bacterial infections of the lungs and skin.

  • Nafcillin. Often used to treat infections caused by staphylococcus bacteria (staph infections).

  • Penicillin V. Used to treat ear infections and tonsil infections. It can also prevent recurrence of rheumatic fever and skin infections from streptococcus bacteria.

  • Penicillin G. Used to treat bacterial infections of the ear, nose, and throat, skin and soft tissues and respiratory tract.

  • Azlocillin. Widely used, though mainly for the treatment of pseudomonas infections that lead to urinary tract infections, sepsis and pneumonia.

  • Mezlocillin. Commonly used to treat infections of the lungs, urinary tract and skin.

  • Oxacillin. Commonly used to treat penicillin–resistant staph infections.

  • Piperacillin. Used to treat moderate and severe infections.

Related allergies and conditions

Several kinds of conditions are specifically related to penicillin allergies. These include:

  • Group B streptococci (GBS). Some physicians recommend that some pregnant women take penicillin to avoid passing on GBS (bacterial infection that can harm newborns) to their babies. Though penicillin is the first choice for treatment, pregnant women who are allergic to penicillin can treat this condition with other antibiotics as well.

  • Cephalosporin allergy. Part of the basic chemical structure is the same for both the penicillin and cephalosporin (antibiotics that include cefaclor and cephalexin) family. Because of the chemical similarities, a person with a penicillin allergy may have a cross-reaction when taking cephalosporins. This is a rare type of condition, however.

  • Penicillium allergy. Inhaled mold is one of the most common types of allergens associated with hay fever (allergic rhinitis). One type of mold, penicillium, is used to make the drug penicillin. Some individuals are allergic to penicillium when it is inhaled. However, there is no relationship between a respiratory allergy to penicillium and an allergy to the drug penicillin. Individuals who are allergic only to penicillin will not experience any type of allergic reaction when they inhale this type of mold.

Because of similarities in symptoms, the cause of a penicillin allergy may go unrecognized. A penicillin allergy shares symptoms with many other common allergies, including:

  • Allergic rhinitis. Inflammation of the mucous membrane that lines the nose, due to an allergic reaction to pollen, dust or other airborne substances. Symptoms include runny nose and itchy eyes.
  • Allergic conjunctivitis. Inflammation of the tissue lining the inside of the eyelid caused by an allergic reaction. Symptoms include itchy eyes.
  • Allergic sinusitis. Inflammation of the lining of the sinus cavities in the face caused by an allergic reaction. Symptoms can include runny nose and nasal congestion.
  • Food allergy. An allergic reaction to a specific type of food (e.g., peanuts, seafood).  Symptoms include nausea, itching and hives.

Penicillin is generally not taken if the patient has a history of bleeding problems, kidney disease, liver disease, infectious mononucleosis or stomach or intestinal diseases. Patients with these conditions should always discuss the use of penicillin with their physician before taking the drug.

Signs and symptoms of penicillin allergy

The signs and symptoms of a penicillin allergy may range from mild to severe. Several of the common signs and symptoms of an allergic reaction to penicillin are not life–threatening. Still, people experiencing any of these symptoms after taking penicillin should consult a physician. The physician should be able to prescribe an alternate medication. Common symptoms include a rash, hives, itchy eyesand angioedema (swelling of thetongue, lips or face).

Some individuals may experience more severe reactions to taking penicillin. Anaphylaxis is a rare, severe allergic reaction that involves two or more body systems. It often begins immediately after an individual has been exposed to a particular allergen. Signs of an anaphylactic reaction include:

  • Dizziness
  • Increased thirst
  • Increased weakness or tiredness
  • Weight loss
  • Wheezing
  • Faster or slower pulse
  • Blue skin, lips or fingernail beds (cyanosis)
  • Nausea or vomiting
  • Diarrhea
  • Seizures
  • Unusual bleeding or bruising

The most sensitive individuals may experience a potentially life–threatening condition called anaphylactic shock, which usually involves the constriction of the air passageways and a dangerous drop in blood pressure. Symptoms include:

  • Shortness of breath
  • Tightening in the chest or throat
  • Choking
  • Loss of consciousness

Individuals who exhibit signs of anaphylaxis or anaphylactic shock should seek immediate medical help.

Because penicillin is used to treat infection, and a common symptom of infection is a rash, many people mistakenly believe they have an allergy to penicillin when a rash develops after a shot. Common drug side effects, such as nausea, can also be misperceived as signs of an allergy. Unlike drug allergies, drug side effects do not involve an immune system reaction.

Individuals who suspect a penicillin allergy for any reason should consult a physician. A physician can perform a skin test or other tests to diagnose whether a penicillin allergy is present or not.

Certain types of penicillin are known to cause dark or amber urine, pale stools, stomach pain or yellow eyes and skin (jaundice). These include amoxicillin, clavulanate, azlocillin, mezlocillin, oxacillin and piperacillin. Though these signs and symptoms do not indicate the presence of an allergy, they may signal the presence of a liver disorder, and therefore should be reported to a physician.

Treatment options for penicillin allergy

An allergic reaction to penicillin usually results in symptoms that affect the nose, throat, lungs, skin and gastrointestinal tract. These symptoms can be treated with several types of medications, including:

  • Antihistamines. Medications that provide relief for hives, sneezing, runny nose and gastrointestinal symptoms. Antihistamines directly counteract the effects of histamines, which are chemicals responsible for most penicillin allergy symptoms. With mild symptoms, these drugs are usually administered orally. For more severe allergic reactions, a physician may recommend an injected form of the drug.
  • Bronchodilators. Medications that open the airways of the lung, relieving symptoms such as shortness of breath or wheezing. They may be recommended for people whose penicillin allergies trigger asthma attacks or asthma–like symptoms. They are usually breathed directly into the lungs using an inhaler.

  • Corticosteroids. Medications that reduce inflammation. These medications can be taken regularly to prevent allergic reactions.

  • Epinephrine injection. A synthetic form of adrenaline that, when injected, is a powerful bronchodilator, opening breathing tubes and restoring normal respiration quickly. It is usually reserved for the most severe allergic reactions that involve anaphylactic shock. Most physicians recommend that individuals who are susceptible to severe penicillin reactions carry an injection of epinephrine with them at all times and understand how to self–administer the drug. A medical alert bracelet or necklace is also a good recommendation for these individuals.

Over time, most people who suffer from a penicillin allergy will eventually lose their sensitivity, or have symptoms decrease. However, most physicians recommend that those people who have had an allergic reaction to penicillin avoid the drug for the rest of their lives.

Some people can have their reaction to penicillin reduced through desensitization. This type of treatment involves a person being exposed to small amounts of penicillin every few minutes, gradually weakening the body’s sensitivity to the drug for a short period. Typically, this type of treatment only works long enough to give the patient a full dose of penicillin. The next time penicillin is required, the patient must be completely desensitized again. This type of treatment carries some risk, and is generally used only if penicillin is absolutely necessary. Desensitization should only be performed by an experienced physician in a medical facility where the patient can be closely observed.

Prevention methods for penicillin allergy

The simplest and most effective way to avoid an allergic reaction to penicillin is to avoid taking penicillin and other forms of the drug. Unlike food allergies or additive sensitivities, individuals with a penicillin allergy can avoid their allergen with relative ease. People with this allergy should inform all healthcare providers (including dentists) of their condition. Individuals with a severe penicillin allergy should wear a medical alert bracelet or necklace to inform healthcare workers of their condition.

To better avoid exposure, individuals with a penicillin allergy should also learn the other names of the medications in the penicillin family. These include:

  • Amoxicillin
  • Ampicillin
  • Dicloxacillin
  • Nafcillin
  • Penicillin G
  • Penicillin V
  • Azlocillin
  • Mezlocillin
  • Oxacillin
  • Piperacillin

Some individuals who are allergic to penicillins will also be allergic to the cephalosporin family of antibiotics, which are chemically similar to penicillins. A physician can use an allergy skin test to make the determination and can prescribe an alternate type of antibiotics if this cross-reactivity is present.

Although there are steps people can take to avoid exposure, accidental contact with penicillin can occur and highly susceptible individuals should be prepared. Physicians often recommend that allergic individuals who are highly sensitive to penicillin carry an epinephrine shot with them at all times. These shots are used to counteract the affects of the potentially life–threatening condition known as anaphylactic shock. These allergic individuals should know how to correctly self–administer their medication and family and friends should also be instructed on its use. Parents of children with penicillin allergies should know how to properly treat a severe reaction in their child and also inform school officials and other caregivers of these procedures.

Some physicians believe that children require repeated exposure to penicillin in order to develop sensitivity to the drug. Children who have a pre–existing respiratory or skin allergies are not more likely to have a penicillin allergy, but rather are more likely to experience a severe reaction if they do have a penicillin allergy. Penicillin allergies are more common in children than adults.

Some people who are in great need of a penicillin treatment, but who have an allergy to the drug, can undergo a process known as desensitization. With this type of treatment, a patient is exposed to small amounts of penicillin every few minutes (usually intravenously). This exposure weakens the body’s sensitivity to the drug gradually, and only for a short period of time.

Desensitization is designed to work only long enough to allow a patient to receive a full dose of penicillin. If penicillin is required again in the future, the patient must undergo the desensitization process again. Because this type of treatment involves exposing a person to an allergen, it does carry a certain amount of risk.

Penicillin is capable of passing through breast milk, though usually in a highly diluted form. These slight amounts can still cause allergic reactions, diarrhea, fungal infections and skin rashes in some infants. Breastfeeding women should consult their physicians before using penicillin.

Questions for your doctor

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about penicillin allergies:

  1. How will I know if I am allergic to penicillin?
  2. What tests will you use to determine if I am allergic to penicillin?
  3. Is a penicillin allergy dangerous to my overall health?
  4. If I am allergic to penicillin, are there other drug treatments I can use instead of penicillin?
  5. Are there other drugs I should avoid?
  6. Will I need to carry an allergy kit with me at all times?
  7. Am I a candidate for desensitization?
  8. If I was desensitized to penicillin once, can I now use penicillin safely?
  9. Is it likely my children will develop a penicillin allergy as well?
  10. Is it likely my child will out grow this allergy?
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