Drug Allergies

What are Drug Allergies?

Adverse reactions to medications are common, yet everyone responds differently. One person may develop a rash or other reactions when taking a certain type of medication, while another person on the same drug may have no adverse reaction at all.

Only about 5% to 10% of these reactions are due to an actual allergy to the medication.

An allergic reaction occurs when the immune system overreacts to a harmless substance, in this case a medication, which triggers an allergic reaction. “Sensitivities” to drugs may produce similar symptoms, but this type of reaction would not involve the immune system.

Certain medications are more likely to produce allergic reactions than others.

Some common examples are:

Antibiotics (such as penicillin)

Aspirin and non-steroidal anti-inflammatory medications such as ibuprofen


Monoclonal antibody therapy



Reactions to medications range from vomiting and hair loss with cancer chemotherapy to upset stomach from aspirin or diarrhea from antibiotics. If you take ACE (angiotensin converting enzyme) inhibitors for high blood pressure, you may develop a cough or facial and tongue swelling.

In many cases, it can be difficult to determine if the reaction is due to the medication or something else. This is because your symptoms may be similar to other conditions.

The most frequent types of allergic symptoms to medications are:

Skin rashes, particularly hives


Respiratory problems

Swelling such as in the face


(Anaphylaxis is a serious allergic response that often involves more than one system of the body like swelling, hives, lowered blood pressure or in severe cases, shock. Anaphylactic shock is a severe condition and if it isn’t treated immediately, it can be fatal.)


If you have side effects that concern you or you suspect a drug allergy has occurred, be sure to contact your physician. If your symptoms are severe, seek medical help immediately. A serious anaphylactic reaction requires immediate medical attention because the results can be fatal.

If you have a history of reactions to different medications or if you have a serious reaction to a drug, an allergist/immunologist, often referred to as an allergist, has specialized training and testing experience to diagnose the problem and help you develop a plan to protect you in the future.

In most cases of adverse reactions, your physician can prescribe an alternative medication. For serious reactions, your doctor may provide antihistamines, corticosteroids or epinephrine.

When no alternative is available and the medication is essential, a desensitization procedure to the medication may be recommended. This involves gradually introducing the medication in small doses until the therapeutic dose is achieved.

Make sure your physician, dentist and pharmacist are kept current regarding your drug allergies. This will help determine which medications should be avoided