Thanks for posting your query.
It is important to rule out pityriasis versicolor from your symptoms. The other one that needs evaluation is erythrasma which presents in the body folds as well-demarcated, brown-red macular patches. The skin has a wrinkled appearance with fine scales.
Pityriasis versicolor is a fungal disease caused by a type of yeast that naturally lives on your skin. When the yeast grows out of control, the skin disease, which appears as a rash, is the result.
The spots may disappear during cool weather and get worse during warm and humid weather and appears as light or dark patches on face or chest which do not tan with exposure to sun.
KOH examination of the skin scrapings and Wood’s lamp examination may help in confirming the diagnosis.
Hope that this information helps and hope that you will get better soon.
Wishing you good health.