Allergies (Hypersensitivity)

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Notes

Allergies (Hypersensitivity):

  • Some of the individuals are very sensitive to some particles present in the environment.
  • The exaggerated response of the immune system to certain antigens present in the environment is called allergy (allo-altered, erg-reaction).
  • The substances to which such an immune response is produced are called allergens.
  • The common examples of allergens are mites in dust, pollens, and some proteins in insect venom.
  • An allergen is an antigen that causes an allergic reaction.
  • Allergy is a form of an overactive immune response mediated by IgE and mast cells.
  • Allergy is due to the release of chemicals like histamine and serotonin from the mast cells.
  • Symptoms of allergic reactions include sneezing, watery eyes, running nose, and difficulty in breathing.
  • For determining the cause of the allergy, the patient is exposed to or injected with very small doses of possible allergens, and the reactions are studied. 
  • The use of drugs like anti-histamine, adrenalin, and steroids quickly reduces the symptoms of allergy.
  • Allergic reactions begin within a few seconds after the contact with the allergen and last about half an hour.
  • Hay fever and asthma are some common examples of allergies.
  • Anaphylaxis is the classical immediate hypersensitivity reaction. It is a sudden, systematic, severe, and immediate hypersensitivity reaction occurring as a result of rapid generalized mast-cell degranulation.
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