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Drug allergies

Allergic reaction - drug (medication); Drug hypersensitivity; Medication hypersensitivity

Drug allergies are a group of symptoms caused by an allergic reaction to a drug (medicine).

Causes

A drug allergy involves an immune response in the body that produces an allergic reaction to a medicine.

The first time you take the medicine, you may have no problems. But, your body's immune system may produce a substance (antibody) against that drug. The next time you take the drug, the antibody may tell your white blood cells to make a chemical called histamine. Histamines and other chemicals cause your allergy symptoms.

Common allergy-causing drugs include:

  • Drugs used to treat seizures
  • Insulin (especially animal sources of insulin)
  • Substances containing iodine, such as x-ray contrast dyes (these can cause allergy-like reactions)
  • Penicillin and related antibiotics
  • Sulfa drugs

Most side effects of drugs are not due to an allergic reaction. For example, aspirin can cause hives or trigger asthma without involving the immune system. Many people confuse an unpleasant, but not serious, side effect of a medicine (such as nausea) with a drug allergy.

Symptoms

Most drug allergies cause minor skin rashes and hives. These symptoms may occur right away or hours after receiving the drug. Serum sickness is a delayed type of drug allergy that occurs a week or more after you are exposed to a medicine or vaccine.

Common symptoms of a drug allergy include:

Symptoms of anaphylaxis include:

Exams and Tests

An examination may show:

  • Decreased blood pressure
  • Hives
  • Rash
  • Swelling of the lips, face, or tongue (angioedema)
  • Wheezing

Skin testing may help diagnose an allergy to penicillin-type medicines. There are no good skin or blood tests to help diagnose other drug allergies.

If you have had allergy-like symptoms after taking a medicine or receiving contrast (dye) before getting an x-ray, your health care provider will often tell you that this is proof of a drug allergy. You do not need more testing.

Treatment

The goal of treatment is to relieve symptoms and prevent a severe reaction.

Treatment may include:

  • Antihistamines to relieve mild symptoms such as rash, hives, and itching
  • Bronchodilators such as albuterol to reduce asthma-like symptoms (moderate wheezing or cough)
  • Corticosteroids applied to the skin, given by mouth, or given through a vein (intravenously)
  • Epinephrine by injection to treat anaphylaxis

The offending medicine and similar drugs should be avoided. Make sure all your providers -- including dentists and hospital staff -- know about any drug allergies that you or your children have.

In some cases, a penicillin (or other drug) allergy responds to desensitization. This treatment involves being given very small doses at first, followed by larger and larger doses of a medicine to improve your tolerance of the drug. This process should be done only by an allergist, when there is no alternative drug for you to take.

Outlook (Prognosis)

Most drug allergies respond to treatment. But sometimes, they can lead to severe asthma, anaphylaxis, or death.

When to Contact a Medical Professional

Call your provider if you are taking a medicine and seem to be having a reaction to it.

Go to the emergency room or call the local emergency number (such as 911) if you have difficulty breathing or develop other symptoms of severe asthma or anaphylaxis. These are emergency conditions.

Prevention

There is generally no way to prevent a drug allergy.

If you have a known drug allergy, avoiding the drug is the best way to prevent an allergic reaction. You may also be told to avoid similar medicines.

In some cases, a provider may approve the use of a drug that causes an allergy if you are first treated with medicines that slow or block the immune response. These include corticosteroids (such as prednisone) and antihistamines. Do not try this without a provider's supervision. Pretreatment with corticosteroids and antihistamines has been shown to prevent allergic reactions in people who need to get x-ray contrast dye.

Your provider may also recommend densensitization.

References

Celik G, Pichler WJ, Adkinson NF Jr. Drug allergy. In: Adkinson NF Jr, Bochner BS, Burks AW, et al, eds. Middleton's Allergy: Principles and Practice. 8th ed. Philadelphia, PA: Elsevier Saunders; 2014:chap 79.

Grammer LC. Drug allergy. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 254.

Tran TP, Muelleman RL. Allergy, hypersensitivity, angioedema, and anaphylaxis. In: Marx JA, Hockberger RS, Walls RM, et al, eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 8th ed. Philadelphia, PA: Elsevier Saunders; 2014:chap 119.

    • Anaphylaxis

      Anaphylaxis - illustration

      Anaphylaxis is an acute systemic (whole body) type of allergic reaction which occurs when a person has become sensitized to a certain substance or allergen and is again exposed to the allergen. Some drugs, such as those used for pain relief or for x-rays, may cause an anaphylactoid reaction on first exposure. Histamines and other substances released into the bloodstream cause blood vessels to dilate and tissues to swell. Anaphylaxis may be life threatening if obstruction of the airway occurs, if blood pressure drops, or if heart arrhythmias occur.

      Anaphylaxis

      illustration

    • Hives

      Hives - illustration

      Hives are raised red welts of various size on the surface of the skin, often itchy, which come and go. Also called urticaria, hives is usually part of an allergic reaction to drugs or food. The term "dermatitis" describes an inflammatory response of the skin, caused by contact with allergens or irritants, exposure to sunlight, or by poor circulation, even stress. AVOID SCRATCHING. Scratching the rash may spread the inflammation, lead to infection and even leave scars.

      Hives

      illustration

    • Allergic reactions to medication

      Allergic reactions to medication - illustration

      A true allergy to a medication is different than a simple adverse reaction to the drug. The allergic reaction occurs when the immune system, having been exposed to the drug before, creates antibodies to it. On subsequent exposure to the drug these antibodies cause release of histamines. If severe, this reaction can result in a life-threatening situation known as anaphylactic shock.

      Allergic reactions to medication

      illustration

    • Dermatitis, contact

      Dermatitis, contact - illustration

      This picture shows a skin inflammation (dermatitis) caused by contact with a material that causes an allergic reaction in this person. Contact dermatitis is a relatively common condition, and can be caused by many substances.

      Dermatitis, contact

      illustration

    • Dermatitis, pustular contact

      Dermatitis, pustular contact - illustration

      This is a close-up of a dermatitis reaction. It consists of a large, red (erythematous) lesion (plaque) with numerous small pus-filled areas (pustules).

      Dermatitis, pustular contact

      illustration

    • Drug rash, Tegretol

      Drug rash, Tegretol - illustration

      This drug rash was caused by Tegretol. Medications can cause many different skin reactions, with varying rashes.

      Drug rash, Tegretol

      illustration

    • Fixed drug eruption

      Fixed drug eruption - illustration

      Medications can cause many skin reactions. This particular appearance is called a "fixed drug eruption" and was caused by a reaction to ceftazidime. This type of reaction typically recurs in exactly the same location when the person takes the same medication again.

      Fixed drug eruption

      illustration

    • Fixed drug eruption, bullous

      Fixed drug eruption, bullous - illustration

      Medications can cause many different types of skin reactions. This particular appearance is called a "fixed drug eruption". This type of reaction typically happens in the same location when the person uses the same medication again.

      Fixed drug eruption, bullous

      illustration

    • Fixed drug eruption on the cheek

      Fixed drug eruption on the cheek - illustration

      Medications can cause many skin reactions. This particular rash, seen here on the cheek, is called a "fixed drug eruption". This type of reaction typically occurs in the same location when the person uses the same medication again.

      Fixed drug eruption on the cheek

      illustration

    • Drug rash on the back

      Drug rash on the back - illustration

      Many medications may produce allergic rashes. This individual has had an allergic reaction to ampicillin.

      Drug rash on the back

      illustration

    • Antibodies

      Antibodies - illustration

      Antigens are large molecules (usually proteins) on the surface of cells, viruses, fungi, bacteria, and some non-living substances such as toxins, chemicals, drugs, and foreign particles. The immune system recognizes antigens and produces antibodies that destroy substances containing antigens.

      Antibodies

      illustration

      • Anaphylaxis

        Anaphylaxis - illustration

        Anaphylaxis is an acute systemic (whole body) type of allergic reaction which occurs when a person has become sensitized to a certain substance or allergen and is again exposed to the allergen. Some drugs, such as those used for pain relief or for x-rays, may cause an anaphylactoid reaction on first exposure. Histamines and other substances released into the bloodstream cause blood vessels to dilate and tissues to swell. Anaphylaxis may be life threatening if obstruction of the airway occurs, if blood pressure drops, or if heart arrhythmias occur.

        Anaphylaxis

        illustration

      • Hives

        Hives - illustration

        Hives are raised red welts of various size on the surface of the skin, often itchy, which come and go. Also called urticaria, hives is usually part of an allergic reaction to drugs or food. The term "dermatitis" describes an inflammatory response of the skin, caused by contact with allergens or irritants, exposure to sunlight, or by poor circulation, even stress. AVOID SCRATCHING. Scratching the rash may spread the inflammation, lead to infection and even leave scars.

        Hives

        illustration

      • Allergic reactions to medication

        Allergic reactions to medication - illustration

        A true allergy to a medication is different than a simple adverse reaction to the drug. The allergic reaction occurs when the immune system, having been exposed to the drug before, creates antibodies to it. On subsequent exposure to the drug these antibodies cause release of histamines. If severe, this reaction can result in a life-threatening situation known as anaphylactic shock.

        Allergic reactions to medication

        illustration

      • Dermatitis, contact

        Dermatitis, contact - illustration

        This picture shows a skin inflammation (dermatitis) caused by contact with a material that causes an allergic reaction in this person. Contact dermatitis is a relatively common condition, and can be caused by many substances.

        Dermatitis, contact

        illustration

      • Dermatitis, pustular contact

        Dermatitis, pustular contact - illustration

        This is a close-up of a dermatitis reaction. It consists of a large, red (erythematous) lesion (plaque) with numerous small pus-filled areas (pustules).

        Dermatitis, pustular contact

        illustration

      • Drug rash, Tegretol

        Drug rash, Tegretol - illustration

        This drug rash was caused by Tegretol. Medications can cause many different skin reactions, with varying rashes.

        Drug rash, Tegretol

        illustration

      • Fixed drug eruption

        Fixed drug eruption - illustration

        Medications can cause many skin reactions. This particular appearance is called a "fixed drug eruption" and was caused by a reaction to ceftazidime. This type of reaction typically recurs in exactly the same location when the person takes the same medication again.

        Fixed drug eruption

        illustration

      • Fixed drug eruption, bullous

        Fixed drug eruption, bullous - illustration

        Medications can cause many different types of skin reactions. This particular appearance is called a "fixed drug eruption". This type of reaction typically happens in the same location when the person uses the same medication again.

        Fixed drug eruption, bullous

        illustration

      • Fixed drug eruption on the cheek

        Fixed drug eruption on the cheek - illustration

        Medications can cause many skin reactions. This particular rash, seen here on the cheek, is called a "fixed drug eruption". This type of reaction typically occurs in the same location when the person uses the same medication again.

        Fixed drug eruption on the cheek

        illustration

      • Drug rash on the back

        Drug rash on the back - illustration

        Many medications may produce allergic rashes. This individual has had an allergic reaction to ampicillin.

        Drug rash on the back

        illustration

      • Antibodies

        Antibodies - illustration

        Antigens are large molecules (usually proteins) on the surface of cells, viruses, fungi, bacteria, and some non-living substances such as toxins, chemicals, drugs, and foreign particles. The immune system recognizes antigens and produces antibodies that destroy substances containing antigens.

        Antibodies

        illustration

      Talking to your MD

       

      Review Date: 3/14/2016

      Reviewed By: Stuart I. Henochowicz, MD, FACP, Associate Clinical Professor of Medicine, Division of Allergy, Immunology, and Rheumatology, Georgetown University Medical School, Washington, DC. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

      The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
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