Yellow, oily dandruff is often a sign of seborrheic dermatitis rather than standard dry dandruff. I recommend switching to a medicated shampoo containing Ketoconazole (2%) or Selenium Sulfide (2.5%). For best results, massage the shampoo into your scalp and leave it on for 5 to 10 minutes before rinsing to allow the active ingredients to work. Use this 2 to 3 times a week. Avoid scratching, and if the condition does not improve within two weeks, or if your scalp becomes very red and inflamed, please consult a dermatologist, as you may need a prescription-strength topical steroid.