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Drug Allergies
Drug allergies occur when the immune system mistakenly identifies a drug, resulting in an allergic reaction. The most common drugs people are allergic to include antibiotics, such as penicillin, and nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin and ibuprofen. Care should always be taken to inform healthcare providers of any known drug allergies to prevent adverse reactions.
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The most commonly reported drug allergy is to penicillin, with up to 10% of people saying they are allergic to these drugs.
However, less than 10% of these people (or less than 1% of the total population) who are evaluated aren't actually allergic to penicillin drugs. Source: AAFA
What is a Drug Allergy?
A drug allergy, also known as medication allergy or pharmaceutical allergy, is a set of symptoms caused by an immune system reaction to medication. It is important to note that a drug allergy is not the same as drug sensitivity or intolerance, which are non-immune reactions that can occur with any dosage and do not involve the immune system.
Drug side effects are often mistaken for drug allergies. However, side effects are known possible reactions listed on drug labels and do not involve an immune response. In contrast, a drug allergy is an unpredictable and potentially severe reaction by the immune system.
While adverse reactions are somewhat common, only about 5% to 10% of these reactions are due to an actual allergy to the medication.
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Sensitivities vs Allergies
Some patients may have sensitivities to drugs, but these are not the same as allergens. Sensitivities to drugs may produce symptoms like those present in an allergic reaction; however, a reaction due to sensitivity to a medication does not involve the immune system.
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Symptoms vs Allergies
Symptoms of drug allergies are also different from the common side effects one might expect when taking a medicine. For example, having an upset stomach is a common side effect associated with certain classes of medications. When a patient experiences one of these side effects, it does not mean that they are allergic or even necessarily sensitive to the drug. Drug toxicity, which occurs when an individual takes too much of a drug, is entirely different from a drug allergy.
What Causes Drug Allergies?
The terms “drug allergy,” “drug hypersensitivity,” and “drug reaction” are often used interchangeably. Regardless of the etiology, drug reaction includes all adverse reactions related to the medication. Drug hypersensitivity is defined as an immune-mediated response to a drug agent in a sensitized patient. Drug allergy is limited specifically to a reaction mediated by IgE. This process begins when the drug enters the body, and the immune system recognizes it as a foreign substance. In response, it produces antibodies called Immunoglobulin E (IgE). These IgE antibodies are designed to neutralize the drug, which the immune system perceives as a threat.
Drug reactions can be classified into immunologic and nonimmunologic causes. Examples of nonimmunologic etiologies include but are not limited to adverse side effects, drug toxicities, and intolerance. In a nonimmunologic cause, the reactions may be clinically indistinguishable from Type I hypersensitivity (an IgE-mediated response) but do not involve drug-specific IgE. An allergic reaction (an IgE-mediated response) occurs when the immune system overreacts to a harmless substance. In this case, it is the medication itself that triggers an allergic reaction. The body views the medication as a threat and begins producing histamines in response. This rise in histamine levels, in turn, causes the body to develop allergy symptoms.
Are drug allergies genetic?
Can you develop a drug allergy over time?
Most common drug allergies
Drug Allergy Symptoms
If you notice any of these new symptoms after taking a drug, seek medical attention.
Hives
Swelling
Itching
Flushing
Facial swelling
Trouble breathing or wheezing
A new rash, including raised or flat
Tightness in the throat or hoarse voice
Abdominal pain or vomiting
- Some symptoms can occur within minutes or hours. However, some rashes may take up to 6 weeks to develop after starting a new medication.
- Drug allergy symptoms can be similar to other allergic reaction symptoms, so you and your allergist must have a clear action plan for when you start showing signs of an allergic reaction.
- A drug allergy could cause anaphylaxis. Anaphylaxis symptoms include Hives, facial or throat swelling, wheezing, lightheadedness, vomiting, and shock. Most anaphylactic reactions occur within one hour of taking a medication or receiving an injection of the drug, but sometimes, the response may start several hours later. Anaphylaxis can result in death, so it is essential to seek immediate medical attention if you experience these symptoms.
When To Visit An Allergist?
If you experience any allergy symptoms while using medication, even weeks after starting a new drug, it is advisable to consult your allergist.
Drug Allergy Treatment
If you have a history of reactions to different medications or a severe reaction to a drug, an allergist or immunologist has specialized training and testing experience to diagnose the problem and help you develop a plan to protect yourself
In case of adverse reactions, your physician can prescribe an alternative medication for severe reactions; your doctor may provide antihistamines, corticosteroids, or epinephrine.
A desensitization process may be recommended when no alternative is available and the medication is essential. This involves gradually introducing the medication in small doses until the therapeutic dose is achieved.