Ihotesti

Ihotesti is the Finnish term for a group of diagnostic skin tests used in dermatology and allergology to assess the skin’s reactivity to various substances. The main forms are patch testing, skin prick testing, and intradermal testing. Patch testing evaluates delayed-type hypersensitivity and is primarily used to identify substances that cause allergic contact dermatitis. Small quantities of common allergens are applied to the skin under occlusion, usually on the back, and readings are taken at 48, 72, and sometimes 96 hours, with reactions graded from negative to varying degrees of positive.

Skin prick testing detects immediate-type hypersensitivity mediated by IgE. Allergens are introduced into the epidermis with a lancet, and the test is read after about 15 to 20 minutes. Positive reactions indicate sensitization to specific allergens such as pollens, foods, insect venoms, or animal dander and are interpreted in the context of clinical history.

Intradermal testing involves injecting tiny amounts of allergen into the dermis and is typically used when prick testing is negative but diagnosis remains uncertain, or for certain allergens. It carries a higher risk of false positives and is generally performed by specialists.

Interpretation relies on clinical history, exposure, and test results. Factors such as active dermatitis, medications that suppress skin reactions, and age can affect accuracy. Patch testing often uses standardized allergen series and country-specific guidelines to ensure consistency.

Historically developed and refined in the 20th century, ihotesti remains a core tool for diagnosing contact dermatitis, atopic conditions, and other hypersensitivity reactions, guiding avoidance strategies and management.