Skin Prick Test

Allergy is the ability of animals and humans to develop altered responses to foreign substances after repeated exposure. It is a hypersensitivity reaction initiated by immunologic mechanisms.

Spectrum of allergen sources

Allergy- Systems Affected


  • Confirmatory test
  • Simple
  • Rapid
  • Low cost
  • Highly sensitive
  • Reproducible
  • Factors involved in allergy skin testing
  • Quality of allergen extract.
  • Diluting fluid.
  • Preservatives.
  • False positive reactions.
  • Irritating reactions.
  • Negative & Positive controls.

Indications of skin prick tests

  • To confirm atopy, assisting in the diagnosis of asthma
  • Before initiating immunotherapy
  • To monitor progress during immunotherapy
  • Acute Urticaria & Anaphylaxis
  • Occupational Diseases including latex allergy
  • Eczema
  • Some drug reactions: Penicillin
  • Stinging insect anaphylaxis
  • Rhinitis vs Sinusitis

SPT is easy to perform and rarely causes generalized reactions.  A positive SPT indicates the presence of IgE antibodies against that allergen but does not indicate clinical sensitivity. A correlation between the history and SPT is essential.
The results can be unreliable if the patient takes certain drugs, such as anti-histamines and tricyclic anti-depressants.