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Types of drug allergy

Several different types of drug allergic reactions can occur: reactions can range from a rash to joint pain or kidney problems. The body's response can affect many organ systems, but the skin is the system most frequently involved.

Drug allergies can vary greatly in severity. They may be dangerous, as the body's response can happen very quickly with a strong reaction (within 1 to 15 minutes), which can be life threatening, as in anaphylaxis (see below).

In contrast to other types of adverse drug reactions, the number and severity of allergic reactions do not usually correlate with the amount of medication taken. For people who are allergic to a drug, even a small amount of the medication can trigger an allergic reaction. Examples of reactions are:

  • skin rashes and itching
  • fever
  • constriction of the airways and wheezing
  • swelling of the upper throat, which impairs breathing
  • a decrease in blood pressure, sometimes to dangerously low levels

Serum sickness is a delayed type of drug allergy that occurs a week or more after exposure to a medication or vaccine. The immune system misidentifies a medication or a protein in the vaccine as a potentially harmful substance, and it develops an immune response to fight it, causing inflammation and various other symptoms.

Symptoms of serum sickness do not develop until 7 to 21 days after initial exposure to the medication or vaccine. However, people may develop symptoms in 1 to 3 days if they have previously been exposed to the medication or vaccine.

Anaphylaxis is a sudden, potentially life-threatening allergic reaction that involves the whole body. Symptoms can develop within seconds or minutes.

Symptoms of anaphylaxis may include the following:

  • difficulty breathing
  • wheezing
  • rapid or weak pulse
  • irregular heartbeat or palpitations
  • blueness of the skin, including the lips or nail beds
  • swelling of the upper throat
  • fainting, light-headedness, dizziness
  • skin redness, hives, and itching
  • nausea, vomiting, diarrhea, abdominal pain or cramps
  • confusion or anxiety
  • slurred speech

Anaphylaxis is an emergency condition requiring immediate medical attention. Call your local emergency number (such as 9-1-1) as soon as you experience any of these symptoms. Early treatment is crucial!

People with known severe allergic reactions may carry an injection containing epinephrine (e.g., EpiPen, Twinject) or other allergy kit in addition to wearing a MedicAlert bracelet.

All material copyright MediResource Inc. 1996 – 2023. Terms and conditions of use. The contents herein are for informational purposes only. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Source:

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