You need to tell whether it is itchy or not ? if itching present - it can be fungal infection- tinea which is common in these parts of body - During periods - wetness and friction of sanitary napkins and tight undergarments may exacerbate the problem. if itching is not there it may be eczematous dermatitis - the white flakes. besides these - if you have chronic( more than 6 months) problem and white flakes are silvery in appearance - you must visit dermatologist to exclude psoriasis - although it s lesions are more commonly seen in extensors of extremities like knees/elbows/ back etc. at present you can try clotrimazole powder - candid powder or acan powder ( Indian brands) for a wk . keep the area clean and dry . do not use harsh soap or dettol to clean the area (- contact irritants). Use ph balanced vaginal cleanser , and mild topical anti inflammatory cream like dexomethasone - dexomet