Large Finn Chamber^®, like the normal 8 mm one, is an epicutaneous patch test device which provides good occlusion. Made of aluminium, the 12 mm inner diameter provides a 110 mm² test area and about 70 µl volume.

Finn Chambers are available as such (loose) or mounted on Scanpor^® tape, Actavis Norway AS, Norgesplaster, with protective paper backing which is easily peeled away. Chambers with polypropylene coating are available for special purposes.

Allergic reactions to aluminium and Scanpor tape are rare. However, occasional cases of contact sensitivity to aluminium e.g. due to vaccination or hyposensitization of hay fever patients with aluminium precipitated antigens have been reported.

Due to the incompatibility of aqueous mercuric solutions with aluminium, polypropylene coated Finn Chambers should be used when testing mercuric solutions.

Indications

Both the normal and large Finn Chambers can be used for various experimental purposes, such as irritancy studies, sensitization of experimental animals, studying the vasoconstrictor effect of corticosteroids or the influence of low concentrations of irritants on skin barrier function. As exposure of larger skin areas may unnecessarily cause more discomfort to the persons tested, e.g. larger skin reactions, atrophy and scars, the use of large chambers should be restricted to those experiments for which 50 mm² area of the normal Finn Chamber is not sufficient.

Application of the test substances

Semisolids (e.g. petrolatum as the vehicle) are applied directly into the chamber, filling about or slightly more than 2/3 of its volume (about 50 µl of test substance). For liquids a special filter paper disc (Whatman 31ET, diameter 11 mm) is placed into the chamber and saturated (about 50 µl). Excess liquid should be removed e.g. with porous paper. Do not let the filter paper disc dry, because this may result in weak or false negative reactions and the disc tends to slip out during application onto the skin.

Placing the tests onto the skin

The tests are applied to healthy skin, which is to be free of ointments and excessive sebum. If necessary, the skin can be cleaned e.g. by alcohol.

Apply the tape starting with the lower part and pressing the chambers from below to let the air escape. After having applied the tape this way, press each chamber with a semisolid gently with the finger to get an even distribution of the test substance. Rub the tape firmly with the palm against the skin, especially on the corners, to ensure good adherence. The patient should refrain from vigorous activities and taking showers during the tests.

Removing the tests

The tests should be removed in the testing laboratory, since the test sites have to be checked immediately after removal. A ring-shaped depression around each test verifies the occlusion and validates the test.

Note

The skin may react to the removal of the tests with a slight mechanical irritation, indicated by erythema on the area covered by the tape. In connection with ordinary patch testing this irritation seldom has much significance. However, when repeating the tests several times on the same area during a few days' period, this phenomenon has to be given full consideration and the tests should, if possible, be placed on varying sites.