Ultrasound for assessment of allergic and irritant patch test reactions.

The oedema formation of patch test reactions was quantified by high-frequency ultrasound measurement of skin thickness. Patch testing with nickel sulphate, nickel chloride and sodium lauryl sulphate 1, 2, 5 and 10% was performed in 12 individuals with known nickel allergy. Oedema was greater in allergic than in irritant reactions similar in strength according to the clinical reading. In allergic reactions, the oedema appeared more transcutaneous, while in irritant reactions, more superficial. For differentiation of the 2 types of reaction, application of substances for a 24-h period with measurements the following day is preferable. For rating of allergic and irritant reactions, 48 h of application is preferable with measurements performed on the day patches are removed.