Owing to the sites that you have stated, fungal infection
is the most likely possibility.
Sweating can lead to recurrent fungal infections in the area between and under the breasts.
Wear count clothes and undergarments.
Use an antifungal dusting powder regularly in summer's. You can use it twice a day.
At present, you need to apply a topical antifungal
Take oral antihistamines for the itching.
Hope it helps.
Dr Geetika Paul.