What are drug allergies?

A drug allergy is a reaction of the immune system to a specific medicine. Any medication – from common antibiotics to over-the-counter pain relievers and herbal remedies – can trigger a drug allergy. However, certain medications are more likely to produce a reaction.

Symptoms can vary from mild to severe and can affect multiple body systems. In some cases, drug allergies can cause anaphylaxis, a severe and life-threatening reaction that requires immediate treatment from medical professionals. 

Children can be allergic to nearly anything – the food they eat, the liquids they drink, or pollen in the air they breathe. Some children are severely allergic to the medications used to treat other conditions.

Drug allergies affect as many as 1 in 10 children nationwide – and may make treatment for common conditions more challenging. For example, penicillin – a common antibiotic used to treat many bacterial infections – is one of the most frequently reported drug allergies.  Some medications are more rare causes of drug allergies.

We provide care for children with allergic reactions to various medications, including:

• Antibiotics (like penicillin/amoxicillin, azithromycin, cefdinir)
• Over-the-counter pain relievers such as aspirin, ibuprofen (Motrin IB, Advil and others), and naproxen sodium (Aleve)
• Anesthetics
• Anticonvulsants (such as medications for seizures)
• Biologics, such as monoclonal antibodies used to treat certain autoimmune condition
• Chemotherapy drugs used to treat cancer
• Vaccines

Drug allergies are different than medication side effects (such as stomach discomfort after taking an antibiotic) and drug toxicity (caused by taking too much of the medication). 

Signs and symptoms of drug allergies

Symptoms of a drug allergy often occur immediately or within an hour of taking the medicine and range from mild to severe. This can include anaphylaxis, a rare, life-threating reaction that can cause widespread changes in the body including:

• Hives and/or swelling
• Trouble breathing, tightening of the throat and/or airway
• Dramatic drop in blood pressure
• Changes in pulse rate
• Lightheadedness, dizziness
• Nausea, cramps, diarrhea and/or vomiting
• Seizure or loss of consciousness

Less severe symptoms of a drug allergy may appear hours, days or weeks later and include: 

• Skin rash or hives
• Swelling
• Itching

In some cases, symptoms can occur even after the drug is no longer being taken. These may include drug-induced anemia, inflammation of the kidneys, joint pain and a drug rash with swelling. 

Rarely, patients can have a severe drug allergy that affects both the skin and various body systems.  These allergies include Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and drug reaction with eosinophilia syndrome (DRESS). 

Causes of drug allergies

Drug allergies occur when the body mistakenly identifies a medicine as a harmful substance, like a virus or bacteria. In some children, the immune system responds by making immunoglobulin E (IgE), an antibody that attacks the medication, attempting to destroy it and remove it from the body. When the medication is introduced again, IgE recognizes it and causes the body to release chemicals like histamine to cause allergy symptoms. 

Reactions to drugs may also be caused by the body’s T-cells, a type of white blood cell that helps protect the body from infection. T-cells identify the drug as a foreign body and attach to it. In most cases, T-cell reactions are slower than IgE reactions.

Risk factors for drug allergies

There are several factors that may increase a child’s risk of developing an allergic reaction to a drug:

• Genetic factors (i.e., family history of drug allergies)
• Age (less common in infants)
• Repeated or prolonged use of a medicine – particularly at high doses
• Some underlying conditions – such as Epstein-Barr and HIV – are associated with an increased risk of allergic reactions from certain medications

Diagnosis and testing

At Children’s Hospital of Philadelphia, patients suspected of having a drug allergy are assessed by experts in the Drug Reaction Evaluation and Management (DREAM) Program, part of the Division of Allergy and Immunology. The DREAM Program provides comprehensive evaluations for children with suspected drug allergies and helps determine options to safety and effectively manage their conditions. 

Before conducting any drug allergy tests, clinicians will review your child’s medical history and ask a series of questions including:

• Medications of concern: What medication was taken, when, and for what reason
• Their symptoms: What they were, when did they start/stop and how long did symptoms last
• Any treatments: How was the reaction treated
• Their family history: Has anyone else in their family had drug allergies or severe reactions from medications

Depending on the drug suspected of causing your child’s allergic reaction, clinicians may suggest one of more of the following:

• Skin test to assess immediate allergic reactions after exposure
• Blood test to measure specific allergy markers, if indicated
• Drug challenge to re-introduce the medication in a monitored setting and see if the child may be able to tolerate the medication
• Drug desensitization to slowly and safely administer a medication that a child is deemed allergic to, but cannot be avoided to treat his or her condition

There are two types of skin tests – a prick test and intradermal test. For the first, a drop of the suspected drug allergen is placed on the skin, then pricked slightly. For the second, a small amount of the drug is injected under the skin. For either test, if the child develops a red, itchy raised bump, they are allergic to the drug.

In a drug challenge, a patient takes gradually increasing amounts (up to a full dose) of the medication under medical supervision in the Allergy clinic or at the hospital. If the patient has an allergic reaction, they can be treated immediately. If the patient can tolerate a full dose of the medication without any concerning symptoms, they are determined to no longer be allergic to the medication.

Treatment of a drug allergy

Treatment for a drug allergy depends on the symptoms and severity. For children with mild symptoms, clinicians may recommend they simply stop taking the drug. Once the medication leaves the child’s body, symptoms should start to fade. 

Treatments for drug allergies include:

• Antihistamines to block to effects of histamine in the body
• Bronchodilators to relieve symptoms affecting the lungs
• Corticosteroids to reduce chemicals in the body that cause inflammation
• Epinephrine to treat symptoms of anaphylaxis

Outlook for children with a drug allergy

Children with drug allergies can live long and healthy lives, but they do need to be careful to avoid the drug to which they are allergic. That means informing their healthcare providers before any type of treatment, surgical procedure or dental care, ensuring the drug allergy is noted in the patient’s medical record, and carrying information about their drug allergy in their wallet, on their phone, or medical alert jewelry. 

While some drug allergies require life-long avoidance, many drug allergies can resolve over time. Furthermore, children often develop rashes while taking antibiotics to treat an infection, but many times, these rashes are not indicative of a true allergic reaction. 

With penicillin allergies specifically, while up to 10% of children carry a penicillin allergy label, more than 90% of children tolerate penicillin when they are introduced to it again. For children with confirmed penicillin allergy, most children outgrow the allergy, with 4 out of 5 able to tolerate it 10 years after their initial reaction. 

Drug allergy evaluations can help determine if a child is truly allergic to a medication. This would allow them to safely take first-line medications like penicillin for many infections, ibuprofen and acetaminophen for common ailments, and receive medications like anesthetics or chemotherapy, if needed.

Why choose us?

The Drug Reaction Evaluation and Management (DREAM) Program at CHOP is the only comprehensive program in the region – and one of the few in the nation – dedicated to diagnosing and treating children with drug allergies. A core group of physicians, nurses and pharmacists collaborate to offer unparalleled diagnosis, treatment and management for children with drug allergies. Over the past decade, the program has grown to a comprehensive program offering treatment and support for families dealing with drug allergies at multiple sites at CHOP.