Drug Allergies/Sensitivities Health Article

Drug sensitivities

Children may have drug sensitivities to aspirin; other NSAIDs; opiates such as morphine and codeine; and some antibiotics, including erythromycin and ampicillin.

Symptoms of drug sensitivities often are very similar to those of drug allergies and include rashes, urticaria, and angioedema.

Anaphylactoid drug reactions are similar to anaphylactic reactions. However, they are caused by a drug sensitivity rather than a drug allergy and can occur upon the first exposure to a drug. Anaphylactoid reactions can occur in response to the following:

• opiates
• radiopaque dyes (radiocontrast media) used in x-ray procedures; 2–3% of patients have immediate generalized reactions to these dyes
• aspirin and other NSAIDs in some people, usually adults
• polymyxin
• pentamidine

Demographics

Anyone can develop an allergy to any drug at any time. It is not clear why some children develop allergies to drugs that are well tolerated by most people. It is estimated that up to 10 percent of all people develop allergies to penicillin or other antibiotics at some point in their lives. Those taking multiple medications or frequent courses of antibiotics appear to be more at risk for developing drug allergies.

The most common drug sensitivity is to aspirin. Nearly 1 million Americans, primarily adults, are sensitive to aspirin. However, many medications, including aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (Advil, Motrin, and others), can trigger an asthma attack in children. Asthma is a common chronic respiratory condition in children. Attacks occur when the air passages from the lungs to the nose and mouth are narrowed causing difficulty breathing. Aspirin and aspirin-like medications are common triggers for asthma attacks in as many as 30 percent of asthmatic children.

When to call the doctor

A physician should be consulted whenever a child has an allergic reaction or sensitivity to a drug. The parent or caregiver should seek emergency assistance if a child has a severe or rapidly worsening allergic reaction to a drug that includes wheezing, difficulty breathing, or other symptoms of anaphylaxis.

Diagnosis

It is important to distinguish between an uncomfortable but mild side effect of a drug and an allergic reaction or sensitivity which could be life-threatening. A drug allergy or sensitivity most often is diagnosed by discontinuing the drug and observing whether the symptoms disappear.

Following a drug reaction the parent should describe the exact course of the reaction; the type of symptoms, when they occurred, and how long they lasted; and whether the child had previously been exposed to the drug. A previous allergic-type reaction to the medication usually is considered diagnostic of a drug allergy. A reaction upon a child's first exposure to the drug is probably a drug sensitivity.

Further diagnosis of a drug allergy may depend on the following:

• a complete medical history, including all drugs taken in the past month, when and how the child received certain drugs, and previous drug reactions
• whether the drug is known to cause allergic reactions
• a family history of drug allergies
• the timing of symptom-onset following drug exposure
• the timing of symptom-disappearance after discontinuing the drug
• the type of rash
• involvement of joints, lymph nodes, or liver
• associated viral infections
• other concurrent medications
• the presence of a chronic disease

Allergy tests

Skin prick tests or intra dermal tests to demonstrate IgE allergies are standardized for very few medications. Penicillin testing is standardized and can be used in extreme situations. Incremental drug challenge tests are also available for several drugs. These tests differ from tests for IgE antibodies but are still useful for demonstrating drug sensitivities. They must be done cautiously as patients are likely to have reactions during the challenge.

The allergist injects a tiny amount of the drug under the skin. If the child is allergic to the drug, swelling and itching occur at the site of injection within 15 to 20 minutes. Skin tests can be used to test for only a few drug allergies, for example, for penicillin and closely related antibiotics. Incremental challenge tests are performed for insulin, streptokinase, chymopapain, and antiserum.

Patch tests may be used to test for allergies to drugs that are applied to the skin such as topical antibiotics. A patch containing a small amount of the drug is applied to the skin to test for a localized reaction.

Desensitization is a test in which the allergist gives the child a tiny dose of the drug—as little as 0.001 or 0.00001 of the usual dose—in its usual form—orally, topically, or by injection. Gradually the dose is increased, and the child's reaction of observed. This procedure is done only in life-threatening situations, however, and only under close observation.