How Is Arms And Back Itching With Dryness Causing Dark Skin Treated?

i travelled to argentina recently for 2 weeks, after the first few nights there i felt a strong itch on my arms, thought they might be bed bugs or mosquito bites, light pinky and a bit dry. Then i realised it was spreading everywhere mostly on my back and left arm,I went to the hospital walk in clinic, and they told me it could be an allergy, so they prescribed a cream with abit of something-zone like 0.1% and allergy pills. The weekafter i went to the coast and got very dark, i ocassionally put sun screen, now wheni got back these spots are pale but getting bigger on my very dark skin. i worried that this is vitilgo.