.hi,small grey patches on the trunck and on the back can be tinea versicolor
not the dry skin
.if it is due to dry skin,by applying moisteriser they would have disappeared by now
Tinea versicolor is a fungal infection
where u find hypopigmented patches with fine scales on them.it is caused by fungus named malassesia furfur .wet condtions,tight clothing excessive humidity aggrevates the disease.
it can be best treated by flucanozole 400mg stat tablet and application of candid-tv shampoo 15 minutes before bath .it is more prone for recurrences