Allergic Reaction

An allergic reaction is a set of symptoms that the body develops in response to a foreign substance. An allergic reaction occurs when the body becomes hypersensitive to a substance, such as a drug, dust, or pollen. The reaction can be localized—in an isolated place in the body—or widespread. A severe allergic reaction, called anaphylaxis or anaphylactic reaction, can be life threatening. Notify your doctor immediately if you develop any symptoms of an allergic reaction.

What is an allergic reaction?

An allergic reaction is an overactive or misdirected immune response to a foreign substance that does not cause a response in most people. An immune response involves activation of white blood cells and cytokines (substances normally produced in your cells) to protect the body from foreign substances, such as viruses and bacteria. However, the body can become hypersensitive to a foreign substance that it has been exposed to in the past, such as drugs, pollen, or dust. Subsequent exposure will produce an exaggerated immune response.

An allergic reaction may be characterized by itching, hives, skin rash, shortness of breath, or wheezing within minutes to 2 hours after contact with an allergy-causing substance, and in rare instances may occur up to 4 hours later. Anaphylaxis is a rapid reaction that affects the whole body and can be life threatening. Symptoms include red, blotchy skin, increased breathing and heart rate, swelling in and around the mouth and throat, and difficulty breathing. Common causes of anaphylaxis include food, medication, insect stings, and latex. First exposure to a foreign substance does not cause an anaphylactic reaction, but subsequent exposure may.

If you experienced these symptoms or think you are  having an allergic reaction, notify your health care provider immediately. Allergic reactions can occur after taking almost any drug.

Which cancer drugs are likely to cause an allergic reaction?

Allergic reactions have been reported with most cancer drugs, although they are generally infrequent and localized. Chemotherapy drugs that have been reported to cause a systemic allergic reaction in more than 10 percent of patients include:

• Alkeran^® (melphalan)
• Elspar^® (asparaginase) - occurs in more than 30 percent of patients
• Matulane^® (procarbazine)
• Oncaspar^® (pegaspargase) - occurs in more than 30 percent of patients

What are the symptoms of an allergic reaction?

Most drug allergies are local reactions, causing minor skin rashes and hives. However, other symptoms occasionally develop into a life-threatening acute allergic reaction involving the whole body (anaphylaxis). A common type of local allergic reaction that occurs with intravenous (into your vein), or intramuscular (into your muscle), or subcutaneous (under your skin) drug administration is called an injection site reaction. Symptoms occur around the site where the drug was injected.

The symptoms of a local or minor systemic allergic reaction include the following:

Hives are raised, itchy, red blotches, which may be pale in the center and red around the outside. Hives are a common drug reaction usually occurring within 36 hours of drug exposure. Hives rarely last for more than 24 hours. However, on exposure to the drug again, the hives may develop within minutes.

• Swelling
• Rash
• Runny nose
• Asthma symptoms (minor wheezing, cough)
• Itching

The symptoms of an anaphylactic reaction include:

• Difficulty breathing due to constriction of the throat or bronchial tubes, or build up of fluid in your lungs
• Faintness and lightheadedness that does not improve dramatically with lying down (due to very low blood pressure)
• Rapid heart rate
• Swelling, including in the tongue, lips, or mouth, causing difficulty in swallowing or breathing
• Nausea, vomiting
• Abdominal pain (cramping)
• Severe bone aches

How is a drug allergy treated?

Most local and minor systemic drug allergies can be treated. Antihistamines usually relieve mild symptoms (rash, hives, itching). Corticosteroid cream may be applied to the skin to relieve itching and swelling. It can also be given by mouth, intramuscularly, or intraveneously. Bronchodilators such as albuterol may be prescribed to reduce asthmalike symptoms (moderate wheezing or cough).

Anaphylaxis is treated with an injection of epinephrine. Epinephrine (adrenalin) is a natural hormone that is produced by the body. It causes relaxation of the bronchioles (throat) and constricts blood vessels to increase blood pressure. Corticosteroids or antiinflammatory drugs can usually be used as well. A drug that has caused anaphylaxis in the past should be avoided.