Drug Allergy

Overview

A drug allergy is an immune system reaction to a medicine, which can cause various symptoms ranging from mild to severe, including hives, rash, fever, swelling, shortness of breath, wheezing, and anaphylaxis. It is different from drug side effects and drug toxicity, which are listed on drug labels and caused by an overdose of medicine, respectively. Symptoms can occur within an hour of taking the drug or hours, days, or weeks later, depending on the reaction type. Drug allergy can be caused by any type of medicine, but certain drugs are more commonly associated with this condition. Risk factors for drug allergy include a history of other allergies, a personal or family history of drug allergy, increased exposure to a drug, and certain illnesses. To prevent drug allergy, it is important to inform healthcare workers of any drug allergies and to avoid using the problematic drug.

Understanding the disease

Symptoms

The symptoms of a drug allergy may include skin rash, hives, itching, fever, swelling, shortness of breath, wheezing, runny nose, itchy, watery eyes, anaphylaxis, serum sickness, and drug-induced anemia. Less common drug allergy reactions can occur days or weeks after exposure to a drug and may persist even after stopping the drug. Symptoms of anaphylaxis, a severe and potentially life-threatening reaction, include tightening of the airways and throat, nausea or abdominal cramps, vomiting or diarrhea, dizziness or lightheadedness, weak and fast pulse, drop in blood pressure, seizure, and loss of consciousness. If you experience any of these symptoms after taking a medication, it is important to seek medical attention right away.

Risk Factors

The risk factors for developing a drug allergy include a history of other allergies, such as food allergy or hay fever, a personal or family history of drug allergy, increased exposure to a drug due to high doses, repeated use, or prolonged use, and certain illnesses commonly associated with allergic drug reactions, such as HIV infection or the Epstein-Barr virus.

Development

Drug allergies develop when the immune system mistakenly identifies a drug as a harmful substance. This can happen the first time you take a drug or after repeated exposures. The immune system produces specific antibodies to the drug, and the next time the drug is taken, these antibodies cause the immune system to attack the substance. This activity releases chemicals that cause the symptoms associated with an allergic reaction. Some evidence suggests that trace amounts of a drug in the food supply, such as an antibiotic, may be sufficient for the immune system to create an antibody to it.

Assessment and Diagnosis

Triage

If you suspect a drug allergy, you should see a doctor as soon as possible. Symptoms can range from mild to life-threatening, and it is important to seek medical advice to determine the appropriate course of action. If you have mild symptoms, such as a skin rash or itching, you should still consult a healthcare provider to ensure that the suspected drug allergy is identified and managed properly. In cases of severe reactions, such as anaphylaxis, you should seek emergency medical attention immediately, as this can be a life-threatening condition.

Diagnosis

To diagnose a drug allergy, your healthcare provider will typically conduct a physical examination and ask you questions about the onset of symptoms, the time you took medications, and the improvement or worsening of symptoms. They may also order additional tests or refer you to an allergy specialist (allergist) for tests. These tests may include skin tests, where a small amount of a suspect drug is administered to the skin, and blood tests that measure the amount of allergy-causing antibodies in your bloodstream. Keep in mind that these allergy tests can sometimes be falsely positive or falsely negative. Your provider will consider the results of these tests, along with your medical history and symptoms, to determine if you have a drug allergy and the best course of treatment.

Management and Treatment

Complications

Potential complications of a drug allergy include:

1. Anaphylaxis: This is a severe, life-threatening reaction that causes widespread dysfunction of body systems. Symptoms of anaphylaxis include difficulty breathing, nausea, abdominal cramps, vomiting, dizziness, fast pulse, drop in blood pressure, seizure, and loss of consciousness.
2. Serum sickness: This condition may cause fever, joint pain, rash, swelling, and nausea.
3. Drug-induced anemia: A reduction in red blood cells can cause fatigue, irregular heartbeats, shortness of breath, and other symptoms.
4. Drug rash with eosinophilia and systemic symptoms (DRESS): This results in a rash, high white blood cell count, general swelling, swollen lymph nodes, and recurrence of a dormant hepatitis infection.
5. Nephritis: Inflammation in the kidneys can cause fever, blood in the urine, general swelling, confusion, and other symptoms. It is essential to seek medical attention if you experience signs of a severe reaction or suspected anaphylaxis after taking a medication. If you have milder symptoms of a drug allergy, consult your healthcare provider as soon as possible.

Prevention

Prevention of drug allergy involves avoiding the problem drug and taking certain steps to protect yourself. If you have a known drug allergy, the best prevention is to:

1. Stop using the problem drug: Discontinue using the drug causing the allergy.
2. Inform health care workers: Ensure your drug allergy is clearly recorded in your medical records and inform other healthcare providers, such as your dentist or medical specialists. If you experience milder symptoms of a drug allergy, it is recommended to consult your healthcare provider as soon as possible.

Home Remedies

Home remedies for drug allergy focus on managing symptoms and preventing further exposure to the allergenic drug. Suggested home remedies include:

1. Avoiding the problem drug: The best home remedy is to stop using the drug that caused the allergy.
2. Applying cold compresses: For skin rashes and itchiness, apply a cold compress, such as a cool damp cloth or an ice pack, to the affected area for 15-20 minutes several times a day.
3. Taking over-the-counter antihistamines: Antihistamines, such as diphenhydramine (Benadryl) or loratadine (Claritin), can help alleviate itching, swelling, and other allergic symptoms. Follow the instructions on the packaging and consult a healthcare professional before administering to children.
4. Using hydrocortisone cream: For mild skin rashes or itchiness, apply a hydrocortisone cream as directed on the packaging. This cream can help reduce inflammation and itchiness.
5. Taking cool baths: Soaking in a cool bath with colloidal oatmeal or baking soda may help soothe itchy skin.
6. Staying hydrated: Drinking plenty of water can help reduce itchiness and swelling.
7. Wearing loose, comfortable clothing: Avoiding tight or irritating clothing can help prevent further irritation.
8. Avoiding irritants and allergens: Identify and avoid substances that may exacerbate your symptoms, such as certain foods, pollen, or pet dander.
9. Keeping a diary: Tracking your activities, diet, and symptoms can help identify triggers and provide valuable information to share with healthcare professionals. Remember, if your symptoms are severe, worsening, or you experience difficulty breathing, seek immediate medical attention.

Treatment

To treat a drug allergy, the following interventions can be used:

1. Withdrawal of the drug: If you have a drug allergy or likely allergy, discontinuing the drug is the first step in treatment.
2. Antihistamines: Your healthcare provider may prescribe an antihistamine or recommend a non-prescription antihistamine to block immune system chemicals triggered during an allergic reaction.
3. Graded challenge: This procedure involves receiving 2 to 5 doses of the drug, starting with a small dose and increasing to the desired dose. If you reach the therapeutic dose with no reaction, your provider may recommend taking the drug as prescribed.
4. Drug desensitization: If it's necessary for you to take a drug that has caused an allergic reaction, your provider may recommend a treatment called drug desensitization, where you receive a very small dose and then progressively larger doses over several hours or days.
5. Medications: Depending on your allergy, various medications can help reduce your immune system reaction and ease symptoms, such as pills, liquid, nasal sprays, or eyedrops.
6. Immunotherapy: For severe allergies or allergies not completely relieved by other treatment, your provider might recommend allergen immunotherapy through injections or sublingual tablets.
7. Emergency epinephrine: If you have a severe allergy, carrying an emergency epinephrine shot can be life-saving in case of a severe allergic reaction. It is important to seek an accurate diagnosis from a healthcare provider to determine the best course of treatment for your drug allergy. They may conduct a physical examination, ask questions about your symptoms, and order additional tests or refer you to an allergy specialist for further evaluation.

Preparing for medical consultation

To prepare for an appointment regarding a drug allergy, you can take the following steps:

1. Make a list of all the medications, vitamins, or supplements you're currently taking, including doses.
2. Note the specific drug to which you suspect an allergy and describe the symptoms you experienced after taking it.
3. Write down the timeframe and severity of the symptoms you experienced.
4. Include any other symptoms you're experiencing, as they may be related to the drug allergy or another underlying condition.
5. List your medical history, including any allergies or previous adverse reactions to medications.
6. Write down any questions you have for your doctor. By having this information readily available, you can effectively communicate with your healthcare provider during your appointment, ensuring that you receive the appropriate guidance and treatment for your drug allergy.