The causes so far is uncertain. The microbes is called
Pytiriasis orbiculares and everyone has it once in a while during
their lifetime. However, our skin's acidic secretions does not
allow it to stay put for a long time, hence normal ppl will be
fine... but if you have an immunodeficiency (such as HIV or on
steroidal medications), then the chances for the fungi to
proliferate will be better...
They will colonize the area and spread... Other causes would be
excessive sweating (hence the condition appears commonly in
subtropical and tropical region) and excessive production of sebum
oil from the skin (genetically, some ppl have this condition and is
called seboerrhoeic dermatitis)...
