The yellow waxy crusts on the scalp are due to dandruff
and it can cause seborrheic dermatitis of the scalp and face. Use over
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.
Hope it helps.Kind regards.