Seborrheic derm. Ketoconazole is found in shampoos, foams, gels and creams. It's available in over-the-counter products in a 1 percent concentration and prescription products at a 2 percent strength. Some studies show that the 2 percent strength may be more effective. In a small percentage of people, ketoconazole can cause irritation, itching and burning. Prescription promiseb is very effective for seborrheic derm.