Drug Allergy: Symptoms, Causes & Treatment

A drug allergy happens when the immune system mistakenly reacts to a medication as harmful. This immune response can cause symptoms that range from mild to severe.

Also known as a drug hypersensitivity reaction, symptoms may appear within minutes after taking or receiving a medication. They can include itching, red eyes, swelling of the face or throat, and dizziness.

If symptoms of a drug allergy develop, it is important to seek medical attention. Some reactions can become severe and, in certain cases, life-threatening.

Main symptoms

The severity of drug allergy symptoms depends on how strongly the immune system reacts and may include:

1. Mild symptoms

Mild drug allergy symptoms include:

• Itching or redness of the skin

• Skin rashes or small spots

• Red, watery, or swollen eyes

• A runny nose or mild nasal congestion

These symptoms may appear within minutes to about an hour after taking or receiving a medication. Some drug allergy reactions can develop several hours, days, or even weeks later.

2. Severe symptoms

Severe drug allergy symptoms include:

• Swelling of the face, lips, tongue, or throat

• Difficulty breathing or swallowing

• Severe dizziness or fainting

• High fever

• Confusion

• Nausea

• Increased heart rate

If severe drug allergy symptoms occur, it is important to go to the hospital so the reaction can be evaluated and treated.

In some cases, severe symptoms can progress to anaphylaxis, a rapid and potentially life-threatening allergic reaction that requires immediate medical attention.

Confirming a diagnosis

A drug allergy can be evaluated by a primary care provider or allergist based on medical history, medications used, and symptoms.

In some cases, a doctor may recommend a drug challenge, which involves giving small doses of the suspected medication under medical supervision to check for a reaction.

If a reaction occurs, the medication may need to be avoided. The test can also help identify medications that may be safe to use instead.

A drug challenge may not be recommended after a severe reaction, such as significant swelling, trouble breathing, or anaphylaxis, because it could trigger another serious reaction.

In these cases, diagnosis may be based mainly on medical history and previous medication reactions.

Main causes

The main medications that can cause drug allergies include:

• Antibiotics, such as erythromycin, tetracycline, penicillin and related antibiotics such as amoxicillin and ampicillin, as well as sulfonamide antibiotics

• Anticonvulsants, such as carbamazepine, lamotrigine, and phenytoin

• Iodinated contrast media used for imaging tests

• Aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and naproxen

• Pain relievers, such as acetaminophen

• Chemotherapy drugs

Other medications can also cause allergic reactions, including HIV medications such as nevirapine and abacavir, as well as neuromuscular blocking medications such as atracurium, succinylcholine, and vecuronium.

What to do

If you develop symptoms of a drug allergy, the following steps are recommended:

1. Stop using the medication

If symptoms of a drug allergy develop, stop using the suspected medication. This can help prevent the reaction from becoming worse and allow the body to recover.

2. Seek medical attention

It is important to seek medical care promptly so the severity of the reaction can be evaluated and appropriate treatment can be started, such as:

• For mild reactions, antihistamines such as hydroxyzine tablets may be recommended, along with supportive measures such as cold compresses for the eyes, rest, and staying hydrated

• For severe reactions, corticosteroids, bronchodilators, or other supportive medications may be given to help with breathing and stabilize blood pressure

For anaphylaxis, epinephrine may be needed. According to the U.S. Food and Drug Administration (FDA), epinephrine is the life-saving treatment for anaphylaxis, which requires immediate medical attention. Hospital monitoring may also be necessary until vital signs are stable.

3. Avoid the medication

Once a drug allergy has been confirmed, the medication should generally be avoided unless an allergist or other specialist recommends otherwise.

It is also important to tell all health care professionals about known drug allergies. This can help prevent future reactions and allow safer alternatives to be chosen when treatment is needed.

How to prevent a reaction

The most reliable way to prevent another reaction is to avoid the medication that caused the allergy. According to the American Academy of Allergy, Asthma & Immunology (AAAAI), doctors, dentists, and pharmacies should be kept informed about known drug allergies so unsafe medications can be avoided.