Drug Allergies
A drug allergy is a specific type of reaction to a medication caused by the body's immune system. Any undesired and unintended response to a medication is called an adverse reaction to the drug. Approximately 6-10% of all adverse drug reactions are drug allergies. It is estimated that 5% of adults may be allergic to one or more drugs.
Allergic drug reactions occur in a small percentage of individuals, are usually unpredictable, and are unrelated to the way in which the medication treats the illness for which it was prescribed.
Allergic reactions to medications can be immediate or dealyed and may be mild or can progress to anaphylaxis. (see anaphylaxis)
The diagnosis is made on the history, including the time between the medication ingestion and appearance of untoward symptoms, and physical findings (e.g., rash).There is no reliable test for drug allergies.
Treatment:
Immediate treatment will depend on the severity of the reaction.
Mild skin reactions only need symptomatic treatment to make the patient comfortable until symptoms clear. The medications suspected to cause the symptoms should be discontinued and not taken again.In case of a severe reaction see the physician right away, go to the emergency room, or call 911.
Persons with a history of severe reactions should wear a bracelet or pendant saying what the medication they are allergic to. This can be life-saving if a patient is taken to an ER or other medical facility and is unable (or forgets) to tell the doctor about the drug allergy.
Most of the time an alternative medication is available to treat the condition for which the original medication was given. Once in a while patient may have an illness where the drug person is allergic to is the drug of choice. In those rare instances, patients can be ‘desensitized’ to the medication under the care of an allergist.
To make a diagnosis of drug allergy in a particular patient sometimes other drug reactions that can resemble drug allergy have to be differentiated. Those are:
- Side-effects are the most common adverse reactions. These are undesirable side effects from a regular dosage of the medication such as stomach irritation from some antibiotics or drowsiness from antihistamine Benadryl.
- Overdosage/Toxicity: This type of reaction occurs predictably from an elevated blood level of the drug. For example too much aspirin can cause tinnitus (ringing in the ears).
- Drug-Drug Interactions: the effect of one drug is altered by another drug. Drug-drug interaction chances are much higher in patient taking several medications for various conditions.
- Idiosyncratic Reactions are an unexpected response to drug from its usual action. For example, most of the time the antihistamine Benadryl has a side-effect of drowsiness but in some individuals it can cause hyperactivity.
- Photosensitivity: some drugs can make patients sensitive to sunlight energy leading to a rash in sun-exposed areas. Tetracycline is one example.
American Academy of Asthma, Allergy and Immunology
www.aaaai.org
