WHAT IS A DRUG ALLERGY?

All medications have the potential to cause side effects, but only about 5% to 10% of adverse reactions to drugs are allergic. A drug allergy happens when you have a harmful reaction to a medicine you use. Your body’s immune system fights back by setting off an allergic reaction. Most drug allergies are mild, and the symptoms go away within a few days after you stop using the medicine. But some drug allergies can be very serious. Some drug allergies go away with time. But after you have an allergic reaction to a drug, you will probably always be allergic to that drug. You can also be allergic to other drugs that are like it. Symptoms and treatments of different kinds of adverse reactions vary. When this occurs your doctor will want to find out if you have a true drug allergy or if you have another type of reaction that is different in nature.

WHAT ARE THE SYMPTOMS OF A DRUG ALLERGY?

The symptoms of a drug allergy can range from mild to very serious. They include:

• Hives or welts, a rash, blisters, or a skin problem called eczema. These are the most common symptoms of drug allergies.
• Coughing, wheezing, a runny nose, and trouble breathing are other symptoms you can experience.
• Rarely, blisters develop as a result of a drug rash. Blisters may be a sign of a serious complication called Steven-Johnson Syndrome where the surfaces of your eye, lips, mouth and genital region may be eroded.
• Toxic epidermal necrolysis (TEN), where the upper surface of your skin detaches like in a patient who has suffered burns, is another type of severe cutaneous adverse reaction. You should seek medical help immediately if you experience any of these. Certain medications for epilepsy (seizures) and gout are often associated with these severe skin reactions.
• Anaphylaxis is the most dangerous reaction. Symptoms of anaphylaxis include hives, facial or throat swelling, wheezing, light-headedness, vomiting and shock. It can be deadly, and you will need emergency treatment. Symptoms, such as hives and trouble breathing, usually appear within 1 hour after you take the medicine. Without quick care, you could go into shock.

WHAT MEDICINES COMMONLY CAUSE AN ALLERGIC REACTION?

Any medicine can cause an allergic reaction. A few of the most common culprits are:

• Antibiotics
• NSAIDS
• ACE-inhibitors
• Chemotherapy drugs
• Monoclonal antibodies
• Barbiturates
• Insulin
• Anticonvulsants

If you are allergic to one medicine, you may be allergic to others like it. For example, if you are allergic to penicillin, you may also be allergic to similar medicines such as cephalosporins (cephalexin or cefuroxime, for example).

People with AIDS or lupus may be allergic to many types of medicines. The reactions usually aren’t dangerous, but they can make it hard to treat the disease.

Some people-especially those with asthma-can have adverse reactions to common pain relievers such as aspirin and ibuprofen (NSAIDS). These reactions can be severe in people who have asthma.

HOW IS A DRUG ALLERGY DIAGNOSED?

An allergist will diagnose a drug allergy by asking you questions about the medicines you take and about any medicines you have taken in the recent past. It is important to tell your physician about any adverse reaction you experience while taking a medication. Be sure to keep a list of any drugs you are currently taking and make special note if you have had past reactions to specific medications. Share this list with your physician and discuss whether you should be avoiding any particular drugs or if you should be wearing a special bracelet that alerts people to your allergy.

HOW IS A DRUG ALLERGY TREATED?

The best thing you can do for a drug allergy is to stop taking the medicine that causes it. If you are in an emergency, this can save your life. You also should know what to do if you have an allergic reaction. Talk to your doctor to see if you can take another type of medicine.

If you can’t change your medicine, your doctor may try a method called desensitization. This means that you will start to take small amounts of the medicine that caused your reaction. You will then slowly increase how much you take. This lets your immune system “get used to” the medicine. This often requires a hospitalization and/or office visit depending on the severity of the reaction. Once the desensitization is performed you must take the medicine daily or you will re-develop the sensitivity again.

If you have an allergic reaction that threatens your life, you may need to give yourself an epinephrine shot and seek emergency medical treatment. Call 911 right away if you have trouble breathing or if you start to get hives. You may also need to take other medicines, such as antihistamines and steroid medicines. A doctor may put these medicines directly into your vein (IV).

If you have a mild allergic reaction, over-the-counter antihistamines may help your symptoms. You may need prescription medicine if these do not help or if you have problems with side effects, such as drowsiness.