This study will examine the within-tester repeatability and between-tester reproducibility of skin test endpoint titrations performed in those with allergic sensitivities.

Participants will be recruited from the local community. Participants with a previous history of skin prick testing in our lab will not be required to undergo preliminary skin prick testing, as the allergen to be used for skin prick titrations is known. New participants will undergo skin prick testing. The procedures for skin prick testing and skin test endpoint (STE) titration will be guided by the AllerGen CIC Allergen Skin Titration by Epicutaneous Method (Prick) Standard Operating Procedure. Different allergen extracts for the skin prick test or different doubling doses of an allergen in duplicate for the STE will be applied to the forearm, pricked with a lancet, and assessed ten minutes later by measuring the wheal sizes produced. The study will require three visits to the lab (i.e. three testers), each separated by one week and lasting roughly 30 minutes. Each visit will entail the duplicate STE procedure performed by a different tester. If a participant is new to the lab, they will undergo skin prick testing during their first lab visit prior to undergoing the skin prick titration and so, their first study visit may last up to one hour.

Inclusion Criteria:

• must have allergic sensitivities confirmed by a skin prick test (or historically) to at least one of the study allergens

Exclusion Criteria:

• skin condition on the forearms
• if there is a situation where interpretation of skin reactions would be difficult (e.g. sleeve tattoos, scarring)
• regular use of anti-histamines (assessed on a case-by-case basis)

Participants will be recruited from the local community.