Dermatitis causes flaking, scales and sores on the scalp and is considered a result of excessive hair oil production known as sebum. Sebum is excreted by the sebaceous glands associated with all follicle pores. Sebum, in normal quantities, helps lubricate and nourish your hair. Excessive sebum can accumulate trapping dirt and lead to bacteria when acting upon yeast. Bacteria and oil causes stickiness and can produce sores, bumps and pimples.