Patch test is read after –
Patch test 

Patch test is done in cases of contact dermatitis to establish the etiological agent.
This is a simple test involves application of suspected allergen as a patch, usually over upper back.
The patch is removed after 48-72 hours and the reading is done and the skin is examined for any signs of dermatitis (erythema, edema and vesicle formation).
You should also remember that reading should be taken after 20 minutes to 1 hour after moval of patch.
So, two different question can be framed :-

1.Patch test is read after → 2-3 days
2.In Patch test, reading is done after removal of patch → 30 minutes to 1 hour.
2 hours
2 days
2 weeks
2 months