The person with the skin problem had seen several doctors with several different diagnosis given. Topical Nizerol, an antifungal treatment, was ineffective.
Overwhelmingly the members on the forum agreed with my suggestion that this was Pityriasis versicolor. Pityriasis versicolor, also known as tinea versicolor is a disorder that is due to a yeast known as malezzia spp. In some mild cases it will respond to over the counter topicals, but often it will not.
There were a few suggestions of allergy, B vitamin deficiency, vitiligo etc. but these opinions were not supported by other practitioners.
Several practitioners mentioned their own experience with pityriasis versicolor when they lived in hot environments.
Though treatment methods varied, they all agreed that an anti-yeast, anti-fungal protocol was the key to getting rid of pityriasis versicolor using supplements, topical cream/washes and dietary changes.
Because pityriasis versicolor has a tendency to reoccur, especially once the weather heats up again, a proper internal and external program needs to be followed for several weeks after the skin has returned to normal.
For more information about pityriasis go to Pityriasis Treatment page.