Pink allergic skin. Patch on my back.

This is limited details and more precise information is needed about your skin condition which can help in planning a treatment. A thorough history, clinical examination and appropriate laboratory tests will be needed to solve the mystery. Consider seeing a Dermatologist for proper diagnosis and treatment plan. The suggested cause looks appropriate in this setting , I would have been more specific but the photographs are not getting downloaded. It is always good to see a dermatologist as after application of medication the face of the disease changes and then it becomes a lengthy process to find out the exact cause. This leads to investigations and other tests which could have been avoided by a simple consultation at appropriate time.

Your dermatologist will decide a treatment plan for you after a consultation.

Avoid Self Medications.