Tree pollens that trigger allergies tend to be very fine and powdery. The wind can carry them for miles.
Inhaling even small amounts can trigger allergy symptoms.
Trees that often set off allergies include:
The test area is cleaned and labeled using an appropriate skin marker. When multiple tests are being performed there should be a minimum of of 3cm between them. The skin is pricked lightly and quickly vertically through the sample allergen . A new micro lancet should be used for each substance being tested. The excess sample allergen should be removed immediately with an absorbent paper towel.
The wheals should be read after 15-20 minutes. For a positive reaction, the wheal should be >= 3mm in diameter. A valid result also requires a positive histamine reaction >=3mm and a negative saline control reaction of < 3mm.