Introduction
A skin allergy test is a diagnostic procedure used to identify substances (allergens) that trigger allergic reactions. It’s commonly used to evaluate allergies to pollen, food, insect venom, medications, and environmental triggers.
Definition
Testing the skin reaction to a substance by placing a small amount of the suspected allergy causing substance, especially over the forearm, upper arm, or back. Allergens are introduced in the skin through scratching or pricking the surface of the skin.
Purposes
- To identify allergens (pollens, molds, pet dander, dust, mites, foods, etc.).
- To introduce the correct mode of treatment after specification of the allergen.
Types
There are three types of skin tests for allergy identification.
1.Skin Prick Test (Scratch Test)
In this test, a thin needle is used to prick the skin on the fore arm or back with 10-15 different potential allergens. Reactions such as redness can be seen within 15 minutes of exposure with rash or raised round spots (wheels). This test checks for airborne allergens and food and penicillin allergies.
2.Intradermal Skin Test
This is done if skin prick test results are negative or inconclusive. Reactions are seen as presence of wheals; erythema with wheals at least >5 mm in diameter indicates positive response. No response till 15-20 minutes is indicated as negative response. This test checks for allergies to air borne irritants, medications, and insect bites or stings.
3.Patch Test
This test can detect delayed allergic reactions. No needles are used and allergens are applied to patches, which are then placed on the skin of the patient. This test determines the cause of contact dermatitis.
Indications
- Hives (urticaria).
- Allergic response elicited as swelling of the face, lips, or tongue, burning sensations on skin or blisters or generalized itching.
- Skin lesions.
- Contact dermatitis (allergens such as latex, nickel, metals).
Contraindication
- Recent anaphylaxis reaction.
Articles
| Articles | Purpose |
| Allergens (0.1-0.5 mL) | Used to inject and find the reaction. |
| 1-mL syringe or an insulin syringe (26 G or 27 G needle) | To inject allergens intradermally. |
| Patches (if patch test) or bandages | To apply allergens. |
| Alcohol swabs | To disinfect the area. |
| Gloves | To prevent injury and infection. |
Procedure
| Nursing Action | Rationale | |
| 1. | Check physician’s order for allergic test. | For correct patient identification. |
| 2. | Check patient’s medical history, for any antihistamines or steroids prescribed. If in use, it should be stopped 3-7 days before test. | To prevent false reading. |
| 3. | Explain the procedure to the patient. | Wins the patient’s confidence and allays anxiety. |
| 4. | Wash hands and don gloves. | Prevents cross infection. |
| 5. | Skin prick test | |
| Cleanse the area. | To prevent infection. | |
| Place a drop of diluted allergic extract on the skin and then prick or puncture skin through the drop into the epidermis at a 45°. | Excessive amount may show extreme reactions. | |
| A thin needle is used to make 10-15 pricks on the skin of the forearm or back with different allergens and name, date, and time are mentioned. | For correct identification of allergen. | |
| 6. | Intradermal skin test | |
| Take small amount of allergens (1:500 to 1:1000) dilution. | To prevent anaphylaxis reaction. | |
| Cleanse the area (ventral forearm approximately 4 inches below the elbow or intrascapular region) with alcohol swab. | To prevent infection, site selection should be guided by patient comfort. | |
| Make a taut on the area where the allergens have to be injected. | To ease the insertion of allergens. | |
| Hold the syringe close to the skin with the level up. | Facilitates injection at the correct site. | |
| Inject the solution creating 6-10 mm wheal. | Ensures accurate reading. | |
| Give space 0.25-0.5 inch apart if several allergens are introduced. | To prevent the solution from mixing. | |
| Remove the needle and place a cotton ball over the injected site. | To absorb any solution on the skin. | |
| Instruct not to rub/massage the site. | May cause irritation of site and error in reading. | |
| Label each allergen name with date and time. | For correct identification of allergen. | |
| 7. | Patch test | |
| Cleanse the area (intrascapular/back) with alcohol swab and let it dry. | To prevent infection. | |
| Put one inch patch (impregnated with allergen) (e.g., fumes, cosmetics, detergents or clothing fibers) applied to the back. | To test allergen. | |
| Cover the area with patches or gauzes (if injecting allergens) and label properly. | To ensure approximate result. | |
| 8. | Discard the needle into appropriate container as per hospital policy. | To prevent needle stick injury. |
| 9. | Reposition the patient. | Enhances comfort. |
| 10. | Instruct the patient to inform immediately if any discomfort or restlessness occurs. | Prevent risk of anaphylaxis. |
| 11. | Instruct the patient to come after; 48-96 hours (patch test)15-30 minutes (skin prick test)24-72 hours (intradermal test) | Enhances accurate reading. |
| 12. | Document the procedure including the date, time, and solution use, patient’s response, location of the injection site, and teachings given. | Further reference and planning of care to be provided. |
Special Consideration
- Avoid certain acid reducers (e.g., famotidine, ranitidine) and cold medications that may contain antihistamines.
- Do not apply lotions, creams, or perfumes to the test area on the day of testing.
- Shave the area (usually forearm or back) if needed to ensure good contact with allergens.
- Wear loose-fitting, short-sleeved or sleeveless clothing to allow easy access to the test site.
- Tie back long hair if testing is done on the back.
- Review medical history, including asthma, eczema, or recent infections.
- Postpone testing if the patient is experiencing acute illness or severe skin flare-ups.
- Monitor for immediate allergic reactions, especially in patients with a history of anaphylaxis.
- Keep emergency medications (e.g., epinephrine) readily available.
- Inform the patient that mild redness or itching may occur and usually resolves within an hour.
- Avoid scratching the test site to prevent irritation or infection.
REFERENCES
- Annamma Jacob, Rekha, Jhadav Sonali Tarachand: Clinical Nursing Procedures: The Art of Nursing Practice, 5th Edition, March 2023, Jaypee Publishers, ISBN-13: 978-9356961845 ISBN-10: 9356961840
- Omayalachi CON, Manual of Nursing Procedures and Practice, Vol 1, 3 Edition 2023, Published by Wolters Kluwer’s, ISBN: 978-9393553294
- Sandra Nettina, Lippincott Manual of Nursing Practice, 11th Edition, January 2019, Published by Wolters Kluwers, ISBN-13:978-9388313285
- Adrianne Dill Linton, Medical-Surgical Nursing, 8th Edition, 2023, Elsevier Publications, ISBN: 978-0323826716
- Donna Ignatavicius, Medical-Surgical Nursing: Concepts for Clinical Judgment and Collaborative Care, 11th Edition ,2024, Elsevier Publications, ISBN: 978-0323878265
- Lewis’s Medical-Surgical Nursing, 12th Edition,2024, Elsevier Publications, ISBN: 978-0323789615
- AACN Essentials of Critical Care Nursing, 5th Ed. Sarah. Delgado, 2023, Published by American Association of Critical-Care Nurses ISBN: 978-1264269884
- Ernstmeyer K, Christman E, editors. Nursing Fundamentals [Internet]. 2nd edition. Eau Claire (WI): Chippewa Valley Technical College; 2024. PART IV, NURSING PROCESS. Available from: https://www.ncbi.nlm.nih.gov/books/NBK610818/
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