Patch Test
Dermatologists use patch tests to determine the cause of allergic skin reactions and eczema. Patch tests are different from prick tests. Prick tests are allergy tests. They are primarily used to identify causes such as house dust, grass pollen, and animal dander that can lead to allergic rhinitis and asthma. Prick tests have limited value in detecting skin rashes.
In patch tests, suspected substances are used in low concentrations to avoid irritation. This is because an irritant reaction could be mistaken for an allergic reaction, leading to misdiagnosis.
• The patch test is applied to the back. After 48 hours, the test patch is removed from the back. The result of the test is evaluated according to the degree of redness, weeping, and swelling that occurs at the test site on the back. Sometimes, because the allergens react later, the test area is re-evaluated after 96 hours.
• Sun exposure should be avoided before patch testing.
• Swimming and exercise should be avoided after the test.
• After the test, the test area should be kept dry. Do not shower.
*Positive allergy test result (caption below image)
Prick Test
The prick test is performed on patients with persistent and unexplained urticaria (hives) and allergic and seasonal rhinitis. During this test, various allergens (suspect substances) are usually placed on the forearms, and the skin's reaction is evaluated after approximately 20 minutes. Allergic reactions manifest as redness and swelling of the skin. The results of this test indicate whether the patient is sensitive to pollens, trees, grasses, various foods, house dust mites, animal dander, and other allergens.
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