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An Overview of Hypersensitivity


What does hypersensitivity mean?

In its simplest definition, hypersensitivity means an exaggerated or inappropriate response of the body’s immune system. It is an undesirable reaction produced by our body’s immunity, including allergies and autoimmunity. These reactions can be both damaging and uncomfortable.

Hypersensitivity is classified into four main types:


  • Type I = Immediate
  • Type II = Antibody-mediated
  • Type III = Immune complex-mediated
  • Type IV = cell-mediated or delayed-type



Type I

–          most common immune disorder

–          can cause asthma, food allergy, and anaphylaxis



Type II

–          can lead to tissue damage through 3 main mechanisms (direct cellular destruction, inflammation, and disrupting cellular function)

–          can cause anemia, acute rheumatic fever, Goodpasture’s syndrome, Graves’ disease, and myasthenia gravis)


Type III

–          caused by excess production of immune complexes

–          can cause serum sickness, rheumatoid arthritis, Arthus reaction, lupus nephritis, and reactive arthritis


Type IV

–          its cell mediators include T-cells

–          can cause multiple sclerosis and rheumatoid arthritis


Type I hypersensitivity is commonly called an allergic reaction. It is the most common that people experience. It occurs as an outcome of exposure to an antigen. The type of antigens involved are as follows:


  • food (eggs, shellfish, soy, nuts, etc.)
  • medication-induced reaction (antibiotics or antivirals)
  • atopic diseases (asthma and allergic rhinitis)
  • environmental sources (pollen, mold, spores)
  • factors involving animals (insect bites, rats, and cats)


On the other hand, type II is also known as cytotoxic reactions. It involves the destruction of cells bound by IgM or IgG antibodies. Its signs and symptoms can appear in several hours. It usually happens after blood transfusions and in newborns.

Type III hypersensitivity is caused by high levels of antigen-antibody complexes. The aggregation of these complexes happens in various tissues, such as joints, blood vessels, skin, and glomeruli. Meanwhile, type IV hypersensitivity takes 1 or 2 days to appear. Some of the illnesses associated with this type include drug hypersensitivity and contact dermatitis.


Hypersensitivity reactions

The following includes the signs and symptoms of allergies associated with every type of hypersensitivity:

  • hay fever (water eyes and runny nose)
  • eczema (red and itchy skin)
  • asthma (difficulty breathing and coughing)
  • hives (skin rashes)


In type I hypersensitivity, anaphylaxis is the most common that people experience. This allergic reaction can cause the following:

  • noisy breathing
  • dizziness
  • unconscious
  • swollen parts of the face
  • stomach pain
  • vomiting
  • nausea
  • difficulty breathing
  • coughing
  • swelling


Treating allergies or hypersensitivity

Taking medications like antihistamine drugs serves as the main form of hypersensitivity treatment. These drugs or medications can be in the form of nasal sprays, eye drops, or tablets. Corticosteroid medicines are also used to treat symptoms of hypersensitivity.

If medications do not work, immunotherapy is necessary. This therapy is specifically designed for treating allergies. It assists the body in stopping overreacting to allergens of any kind.

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