Dark black patches on face. Possible.

Every time I come to Bangalore my wholeface gets filled with dark patches unlike acne marks. The patches look similar to dark black ink blots on cotton cloth. Sometimes it itches and becomes flaky. My whole face texture wise and complexion wise changes. It becomes puffy and extremely dry. I have tried everything maintaining a healthy diet strictly,drinking at least 3 litres of water,changing and washing my bed sheet,pillow cover,towel,napkin etc. Nothing helps. I started using drinking water from filter for washing my face thinking that Bangalore's water might be responsible but it did not really help. And Every time I go to my hometown my skin becomes clear and texture changes within a week. It feels like I have peeled off some dry flaky black skin mask from my face. Kindly give me some natural affordable solutions. Since leaving Bangalore and completely relying on medicines are not possible.