The tests are removed at the 48th time. A first reading is performed 30 minutes after their removal. The second reading takes place, either at the 72nd hour at the 96th time (with a preference for the latter).
Thus, reading patch tests must be carried out in two stages: 48 and 96 hours (ideally), 48 and 72 hours (if the local organization required this time).
Reading at the 48th time cannot be carried out at the time of the removal of materiel (artifacts variety due to the effect of pressure, occlusion and uplift of the material). It is therefore imperative to not read as 20-30 minutes after removal.
In preparation for the second reading, a precise identification of each test site is essential. The tracking is done using a marking pen (e.g..) (Skin marker Chemotechnique) or a fluorescent highlighter (tracking of sites in light of Wood during the second reading). For Finn Chambers, the Boots Hermal firm has created a "boss of reading", each hole of the corresponding pattern of precise localization of an allergen; Chemotechnique also has his own.
A late reading is always advisable in case complexes (e.g. on the 7th day), because for certain allergens response can become positive that more late (e.g. neomycin, various corticosteroids).