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Skin prick test

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Skin prick test (SPT)

A skin prick test, also known as a puncture or scratch test, is a widely used diagnostic tool in the field of allergy testing. This test helps identify specific substances to which an individual may be allergic, providing valuable information for the management and treatment of allergic conditions. In this comprehensive exploration, we'll delve into the procedure, its purpose, preparation, interpretation of results, potential allergens tested, safety considerations, and the broader context of allergy diagnosis and treatment.

Purpose of Skin Prick Test:

The primary purpose of a skin prick test is to identify allergies in individuals who experience symptoms such as sneezing, itching, hives, or respiratory issues that may be associated with exposure to certain allergens. By introducing small amounts of potential allergens into the skin, healthcare providers can observe the body's reaction and pinpoint specific substances that trigger allergic responses.


The skin prick test is a relatively simple and quick procedure that is typically performed in an allergist's office. Here's a step-by-step overview of the process:

Preparation: The healthcare provider will begin by cleaning a small area on the forearm with alcohol. They will then mark the area with a grid, where each square corresponds to a specific allergen to be tested.

Allergen Application: Small drops of allergen extracts are applied to the marked spots on the grid. These extracts may include common allergens such as pollen, pet dander, mold, dust mites, certain foods, and insect venoms.

Puncture: Using a sterile probe or lancet, the healthcare provider punctures the skin through each allergen drop. This allows a minute amount of the allergen to enter the skin, simulating exposure.

Reaction Observation: The provider will closely monitor the test sites for any immediate reactions. If an individual is allergic to a specific substance, a small raised bump (wheal) accompanied by redness may appear at the test site.

Results: Results are typically available within 15-20 minutes. The size of the wheals and the pattern of reactions are analyzed to determine the presence and severity of allergies.

Common Allergens Tested:

Skin prick tests cover a wide range of potential allergens. Some common categories include:

Pollen: Various types of tree, grass, and weed pollens.

Animal Allergens: Pet dander from cats, dogs, and other animals.

Mold: Different types of mold spores.

Dust Mites: Microscopic organisms commonly found in household dust.

Foods: Common food allergens such as nuts, milk, eggs, and shellfish.

Insect Venoms: Allergens from bee or wasp stings.


It's important to note that the specific allergens tested may vary based on the individual's symptoms and medical history.

Interpretation of Results:

Interpreting the results of a skin prick test requires expertise from a healthcare professional, typically an allergist or immunologist. The size of the wheals and the degree of redness are crucial factors in determining the presence and severity of allergies.

Positive Reaction: A positive reaction is characterized by the presence of a significant wheal and redness at the test site. This indicates that the individual is likely allergic to the tested substance.

Negative Reaction: The absence of a noticeable wheal or redness suggests a negative reaction, indicating that the person is not allergic to the tested substance.

Control Site: To ensure the validity of the test, a control site without any allergen is usually included. This site helps establish a baseline for comparison.

Thresholds for Positivity: The size of the wheal is measured against predetermined thresholds to determine the clinical significance of the allergic response.

Safety Considerations:

The skin prick test is generally considered safe for both adults and children. However, there are some important considerations:

Medication Interference: Certain medications, such as antihistamines, can interfere with the accuracy of the test. It is crucial to follow any pre-test instructions provided by the healthcare provider, including discontinuing specific medications for a specified period before the test.

Local Reactions: While most reactions are localized to the test sites, there is a possibility of a more widespread allergic response. Healthcare providers are prepared to manage any potential adverse reactions, although severe reactions are rare.

Contraindications: Individuals with certain skin conditions, such as eczema or psoriasis, may need alternative testing methods, as these conditions can affect the accuracy of the skin prick test.

Pregnancy and Breastfeeding: Although skin prick testing is generally considered safe during pregnancy and breastfeeding, healthcare providers may take additional precautions and considerations for pregnant or breastfeeding individuals.

Broader Context of Allergy Diagnosis and Treatment:

The skin prick test is just one of several methods used in the diagnosis and management of allergies. Other diagnostic tools include blood tests (specifically IgE antibody tests) and oral food challenges. The choice of method depends on the individual's medical history, symptoms, and the suspected allergens.

Once allergies are identified, healthcare providers work with patients to develop personalized treatment plans. This may include allergen avoidance strategies, prescription or over-the-counter medications to manage symptoms, and in some cases, immunotherapy.


In conclusion, the skin prick test is a valuable and commonly used diagnostic tool for identifying allergies. Its simplicity, quick results, and ability to test a wide range of allergens make it a preferred method for many healthcare providers. While it is generally safe, it is essential for individuals undergoing the test to follow pre-test instructions and communicate any relevant medical history to ensure accurate results.

If you suspect allergies or are experiencing allergic symptoms, consulting with an allergist or immunologist is crucial for a comprehensive evaluation and appropriate management. Understanding specific allergies allows for targeted interventions, improving the quality of life for individuals affected by allergic conditions.

Skin prick test, copyright British Allergy Clinic
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