When will be readings taken for the test image given below
24 hrs and 48hrs
48 hrs and 96hrs
48 hrs and 72 hrs
48 hr and 96hrs
Answer-A: 24 hrs and 48hrs
The image given in the question represents the patch test
- A patch test is a method used to determine whether a specific substance causes allergic inflammation of a patient’s skin. Any individual suspected of having allergic contact dermatitis or atopic dermatitis needs patch testing.
- A patch test relies on the principle of a type IV hypersensitivity reaction.
- Application of the patch tests takes about half an hour, though many times the overall appointment time is longer as the provider will take an extensive history. Tiny quantities of 25 to ~150 materials (allergens) in individual square plastic or round aluminum chambers are applied to the upper back. They are kept in place with special hypoallergenic adhesive tape. The patches stay in place undisturbed for at least 48 hours. Vigorous exercise or stretching may disrupt the test.
- At the second appointment, usually, 48 hours later, the patches are removed. Sometimes additional patches are applied. The back is marked with an indelible black felt tip pen or another suitable marker to identify the test sites, and a preliminary reading is done. These marks must be visible at the third appointment, usually 24–48 hours later (72–96 hours after application). In some cases, reading at 7 days may be requested, especially if a special metal series is tested.