Your symptoms of scalp rashes, itching, and excessive oiliness that improve temporarily after washing are most commonly due to seborrheic dermatitis, a condition related to excess oil production and yeast overgrowth on the scalp, sometimes worsened by sweat, dust, and outdoor exposure. Less commonly, it could be folliculitis or a fungal infection, so proper evaluation is helpful. For long-term control, use a medicated anti-dandruff shampoo (containing ketoconazole, zinc, or selenium) 2-3 times a week, leaving it on the scalp for a few minutes before rinsing, and avoid frequent touching or scratching. Maintain good scalp hygiene, but avoid over-washing, which can sometimes increase oiliness. If itching or inflammation is severe, a doctor may prescribe a short course of medicated lotions to calm the scalp. With regular care and the right products, this condition can be effectively controlled even though it may tend to recur.