Without examination,confirmation of a diagnosis is tough but it can be rash
due to viral infection,contact dermatitis,<span style = 'background-color: #dae8f4'>rash</span>
due to friction rub with clothes, dermatitis (atopic, contact, allergic) or excessive <span style = 'background-color: #dae8f4'>sweating</span>
causing sweat dermatitis.
You may try calamine lotion on the rash
.You should also maintain hygiene and try to keep the area clean and dry, wear loose-fitting cotton clothing. Also use an antibacterial soap or mild soap like dove.Avoid any kind of cosmetics.