Drug allergy is the term for a group
of symptoms caused by an allergic reaction. An allergic reaction occurs when
your immune system mistakes the drug for a harmful substance and mounts an
inflammatory response that actually harms rather than protects you.
When a harmful substance, such as a
virus or bacteria, enters your body, your immune system creates antibodies to
fight off the invading infection. An antibody is a special protein that’s programmed
to destroy one specific substance.
Antibodies are also called
immunoglobulins. There are different kinds of immunoglobulins. For example,
immunoglobulin A (IgA) concentrates in tears and saliva and helps to guard
these entrances to the body. IgM is very effective at marking bacteria as
invaders and telling cells to kill them.
The immunoglobulin most often
responsible for the symptoms of an allergy is IgE. IgE tells your white blood
cells to release histamine, which in turn causes many of your symptoms.
Once your immune system has
programmed antibodies to recognize and defend against a specific substance,
those antibodies are always ready to multiply quickly and go to action whenever
the substance is detected. This is how you develop immunity to specific illnesses.
It’s also how you develop allergies to specific substances, such as a
Anyone can develop an allergy
to a drug or other substance. It can happen at any age. You might become
allergic to a drug you’ve used many times before without any adverse reactions.
The reasons why people develop drug allergies are not fully understood.
However, the following factors can increase your risk:
- a weakened immune system from conditions such as HIV/AIDS or
- other allergies
- taking several drugs at the same time
- taking frequent doses of the same medication
- taking a drug that is similar to one you’ve previously had an
allergic reaction to
You are at greater risk for a
severe allergic reaction to a medication if you have
- heart disease
- high blood pressure
You can develop an allergy to almost
any drug. Some drugs are involved in allergic reactions more often than others.
- penicillin and antibiotics similar to penicillin (such as
ampicillin and amoxicillin)
- sulfa drugs
- insulin (especially if from an animal source)
- cephalosporins (another type of antibiotic)