Not very long. The skin prick and intradermal tests are performed in the allergist’s office and take about 20 minutes total. Your skin may start to show reactions to certain allergens such as foods, environmental allergens or insect venoms.
Patch tests are used to identify if a chemical may be the cause of delayed skin rashes. The patches are applied and worn for about 48 hours and then removed.
Blood tests results may take up to a week to return from the laboratory.