Overview, Causes, & Risk Factors
An allergic reaction to a medication is an unintended immune response to the
medication. Symptoms can vary from a mild rash to shortness of breath to death.
It is important to understand the difference between a medication allergy and
a side effect caused by a medication.
What is going on in the body?
An allergic reaction
when a person's immune system reacts to the presence of a foreign substance. It
is an attempt by the body to get rid of the substance. In the case
of an allergic reaction to a medication, this response is harmful. It sometimes
causes serious symptoms.
Side effects are adverse events that happen to a person as a result
of taking a particular medicine. Side effects that are common to medicines
diarrhea, vomiting, headache, and lightheadedness. In some cases, these
will subside even if a person continues to take the medication.
What are the causes and risks of the condition?
An allergic reaction does not usually occur the first time a person is exposed
to the medication. It is only after the body learns to recognize the substance
that an immune system reaction is triggered. Almost any medicine can cause a
reaction. However, allergic reactions are quite rare considering the number of
over-the-counter medicines and
medications that are commonly prescribed.
Medications that are most likely to produce adverse reactions include the
anticonvulsants, which are used to treat seizures
barbiturates, which are used to provide sedation
iodine, which is used in antiseptics and contrast media for some X-ray
novocaine and similar
penicillin and related antibiotics, such as amoxicillin
sulfa medications, which are also antibiotics
Symptoms & Signs
What are the signs and symptoms of the condition?
Symptoms of an allergic reaction to a medication can include the following:
which is a very severe reaction that can lead to death
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hives, which are
multiple small, itchy, swollen areas on the skin
are an unusual awareness of the heart beating within the chest
shortness of breath
swelling of one or more parts of the body
Other symptoms may also occur in some cases.
Diagnosis & Tests
How is the condition diagnosed?
Diagnosis of an allergic reaction begins with a medical history and physical
exam. The healthcare provider will ask about recent medication use.
Prevention & Expectations
What can be done to prevent the condition?
There is no way to prevent the development of an allergic reaction to
a medication. Once a reaction has occurred, an individual should avoid that
particular medicine. Rarely, a person will need to take a medication even if
he or she is allergic to it. In those cases, the person can be pretreated with
medicines that prevent the allergic response. These
medicines include steroids, antihistamines, and epinephrine.
What are the long-term effects of the condition?
There are few long-term problems associated with an allergic reaction. In a few
cases, the reaction will include severe asthma or shock. However, most people recover quickly.
What are the risks to others?
Allergic reactions are not contagious. They pose no risk to
Treatment & Monitoring
What are the treatments for the condition?
Treatment includes measures to control the symptoms
until the medicine is out of the bloodstream. Antihistamines are
used to relieve rash,
hives, and itching. Prednisone or other
are also used to keep more serious symptoms in check. These medicines can be
or applied to the skin.
symptoms can be controlled with medications to open the airways. Injections of
the medication epinephrine are used to treat severe allergic reactions.
What are the side effects of the treatments?
Antihistamines can cause
drowsiness. Prednisone can cause stomach problems,
sleep problems, and mood swings. These side effects are generally very mild.
Medications used to open the airways can cause shakiness and abnormal heart
rate. These tend to be mild. Epinephrine can cause significant anxiety and
shakiness, as well as an abnormal heart rate. This medication is often
administered in the provider's office or in the emergency department.
What happens after treatment for the condition?
Once a person has had an allergic reaction to a medication, he or she
should avoid that medication. Also, a person should always inform
healthcare providers of any medication allergy. People with severe reactions
should carry medical alert cards or wear
ID bracelets. These devices help inform providers of the allergy in emergency
It is important not to report a side effect as an
allergy. People who have had side effects from medicines may safely take them
again if they are seriously ill and need that particular medicine. Generally,
medicines to which a person is allergic will be avoided except in
life-threatening diseases for which there are no other effective
How is the condition monitored?
Any new or
worsening symptoms should be reported to the healthcare provider.