What is a drug allergy?
A drug allergy is an allergic reaction to a medication. When the drug enters
the body, it triggers a response by the immune system, which creates
specific IgE antibodies (proteins made by the immune system to fight specific
antigens). The body becomes sensitized, and when the drug is taken again, the
IgE antibodies go into action, releasing large amounts of histamine that
attempt to expel the drug from the body.
What are the symptoms of drug allergy?
Symptoms can range from mild discomfort to life-threatening conditions. Many
drugs can cause irritation such as an upset stomach; however, during an allergic
reaction, histamines are released and can cause a variety of symptoms, including
hives, skin rash, itchy skin or eyes, congestion, and swelling in the mouth and
throat. Symptoms of more severe reactions include difficulty breathing,
blueness of the skin, dizziness, fainting, anxiety, confusion, rapid pulse,
nausea, diarrhea, and abdominal disturbances.
Which drugs most often cause an allergic reaction?
The most common cause of drug allergies is penicillin. Other antibiotics
similar to penicillin also cause a large number of drug allergies.
Other drugs found to cause reactions that do not involve IgE
antibodies (non-IgE-mediated drug reactions) are sulfa drugs, barbiturates,
anticonvulsants, aspirin, non-steroidal agents, and contrast dye material.
How are drug allergies diagnosed?
Drug allergies are diagnosed by a careful review of the patient’s medical
history and symptoms by a physician. If an allergy to an antibiotic such as
penicillin is suspected, your doctor may do a skin test to confirm the
allergy. However, skin testing does not work on all drugs and in some cases
could be dangerous. Because of the potential risk associated with a reaction, if
a patient has had a severe, life-threatening, allergic-type reaction to a
particular drug, doctors will not consider that drug a viable treatment option,
and will not usually conduct tests to determine if the initial reaction was a
"true" allergic response.
How are drug allergies treated?
The primary concern when treating drug allergies is relieving the symptoms.
Common symptoms such as rash, hives, and itching can often be controlled with
antihistamines and occasionally corticosteroids. For coughing and lung
congestion, adrenergic bronchodilators may be prescribed. For more serious,
anaphylactic symptoms (life-threatening reactions, including difficulty breathing
or loss of consciousness) epinephrine (adrenaline) is usually injected.
Desensitization is occasionally used for penicillin allergy. This technique
is designed to desensitize your body to particular allergy-causing agents.
Penicillin is injected periodically at increasingly larger levels until your
immune system learns to tolerate the drug.
If a patient is severely allergic to certain antibiotics, alternative
antibiotics will be used.
Living with drug allergies
If you have a drug allergy, you should always inform your health care provider before undergoing any type of treatment, including dental care. It is also a good idea to either wear jewelry (bracelet or necklace) or carry a card that identifies your drug allergy. In cases of emergency, this type of identification could save your life.