Hello,
It can be seborrheic dermatitis. Seborrheic dermatitis is a common skin condition that causes flaky,dry, white to yellowish scales to form on oily areas esp under the nose or anywhere on face. You can treat flaking and dryness with over-the-counter dandruff or medicated shampoos. Shampoo the hair vigorously and frequently (preferably daily). Active ingredients in these shampoos include salicylic acid, coal tar, zinc, resorcin, ketoconazole, or selenium.
If the symptoms persist,then it would be best to get it confirmed from a dermatologist
Hope it helps.Take care and pls do keep me posted on how you are doing or if you have any additional doubts.Kind regards.
Seborrheic dermatitis is the condition which is common for both the locations.Scabies is uncommon in adults on the scalp,while commoner in children.Pediculosis is commoner on the head but not so on chest.