I cannot confirm anything without examination but it can be due to erythrasma.It is a chronic superficial infection of the intertriginous areas of the skin.The typical appearance is well-demarcated, brown-red macular patches. The skin has a wrinkled appearance with fine scales.
It has to be differentiated from contact dermatitis,psoriasis,sweat dermatitis and fungal infections which may mimic it.Wood lamp examination and gram staining are the tests for its diagnosis.
So nothing can be confirmed without examination.The standard therapy of erythrasma is antibiotics and antifungals because it is caused by a bacteria C minutissimum.Erythromycin is the drug of choice.Mild steroids are helpful in reducing the inflammation associated with it. But use it only after a dermatologist’s prescription.
I hope it helps.Take care and pls do keep me posted on how you are doing or if you have any additional doubts.Kind regards.