Hypersensitivity (Hypersensitivity Vasculitis)

Hypersensitivity vasculitis is an extreme allergic reaction

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Hypersensitivity is a general term for an extreme allergic reaction to a drug or substance. The most common type of hypersensitivity, or type 1, is usually marked by a red or purple-ish rash and/or hives.

There are four types of hypersensitivity: Immediate, antibody-dependent, immune complex disease, and delayed-type.

Here's more on the characteristics of hypersensitivity, causes and examples of hypersensitivity, the types of hypersensitivity, and treatment.

Man blowing his nose while out in nature

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Symptoms of Hypersensitivity

Symptoms of hypersensitivity include:

  • A rash that includes purple or brown spots
  • Sores on the lower body
  • Blisters, hives, or open sores or ulcers
  • Hay fever

Type 1 hypersensitivity can cause anaphylaxis, which is an extreme allergic reaction that can be deadly. Symptoms of anaphylaxis include:

  • Abnormal breathing
  • Swollen tongue or swelling in the throat
  • Difficulty talking
  • Wheezing or coughing
  • Stomachache
  • Vomiting
  • Dizziness
  • Fainting

Causes of Hypersensitivity

Hypersensitivity is caused by an extreme immune reaction to a foreign substance or illness. The most common type of hypersensitivity, or type 1, can be caused by everyday interactions with substances like pollen or pet hair. Other types of hypersensitivity can result from medications and chronic medical conditions.

The Four Types of Hypersensitivity

The four types of hypersensitivity are:

Immediate Hypersensitivity (Type 1)

Type 1 hypersensitivity, the most common type, is an immediate allergic reaction ranging from mild to severe. It occurs when the body releases proteins that fight against foreign substances (antibodies) in response to a substance the body is allergic (allergen).

Common allergens that can cause type 1 reactions include:

  • Pet hair
  • Mold
  • Pollen
  • Dust mites

Hypersensitivity Emergencies

If you or a loved one experience a severe allergic reaction, please call your local emergency department immediately. Symptoms of severe immediate hypersensitivity include:

  • A quickly appearing and widespread rash
  • Difficulty breathing or high-pitched breathing sounds
  • Difficulty swallowing
  • Wheezing
  • Chest tightness
  • Trouble speaking
  • Swelling on face or in tongue
  • Loss of consciousness
  • Dizziness
  • Heart palpitations
  • Redness of face
  • Vomiting
  • Diarrhea
  • Anxiety

Antibody-Dependent Hypersensitivity (Type 2)

Type 2 hypersensitivity can take two to 24 hours to appear and is marked by antibodies that can destroy cells and cause tissue damage. Type 2 hypersensitivity reactions can occur during or because of:

Type 2 hypersensitivity can take days to weeks to develop. It is marked by antibodies that combine with proteins and then set into the body's tissues, which results in inflammation (the body's response to foreign invaders).

Immune Complex Disease Hypersensitivity (Type 3)

Type 3 reactions can be a part of inflammation associated with:

  • Arthritis
  • Lupus
  • Serum sickness (a reaction to medications like drugs that prevent organ transplant rejections)

Delayed Type Hypersensitivity (Type 4)

Type 4 hypersensitivity, the second most common type, takes at least two days to develop and is marked by skin redness. Examples include:

  • Poison ivy
  • Contact dermatitis
  • Reactions to diagnostic skin tests

Hypersensitivity Treatment

Treatment of hypersensitivity reactions can depend on type. The most common methods are:

Type 1 treatments include:

Type 2 treatments include:

Type 3 treatments include:

  • Avoiding substances that trigger an allergic response
  • Glucocorticoids (steroids)
  • Antihistamines
  • Drugs to manage autoimmune disorders

Type 4 treatments include:

  • Removal of the offending agent
  • Corticosteroids
  • Fluid therapy in a hospital (in extreme cases)
  • Methotrexate


Hypersensitivity refers to extreme allergic reactions to substances and drugs. The most common type of hypersensitivity, or type 1 (immediate), includes sudden allergic reactions that cause hives or rashes. Treatments for hypersensitivity can range from antihistamines and steroids for inflammation to antibiotics and epinephrine.

14 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  3. Healthdirect. Allergies and hypersensitivities.

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  6. MedlinePlus. Allergic reactions.

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By Neha Kashyap
Neha is a New York-based health journalist who has written for WebMD, ADDitude, HuffPost Life, and dailyRx News. Neha enjoys writing about mental health, elder care, innovative health care technologies, paying for health care, and simple measures that we all can take to work toward better health.