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 occurs 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 include nausea, 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 following: