Thanks for the query,
Probably you are suffering from erythrasma
The other possibility is fungal infection
A photograph would have helped better in diagnosing.
Depending upon the cause you need treatment either with topical antibiotics or antifungals.
Please meet a dermatologist
for exact treatment.
Let me know if you have any other doubt.
you can ask a direct question to me on this forum, following the below link.
Wishing you a good health.