The scalp, like any other skin, needs to be able to "breathe" think of it as an extension of the face. Just as pores on the face can become clogged, hair follicles too can experience obstruction if products are placed directly on them.
Know that you are not alone. Scalp Dryness is a common complaint within the natural hair community. And in some cases you are not to be blamed, it can be related to a genetic lack of sebum production at the scalp level.
In most cases however, scalp dryness may be self induced. When products are placed directly on the scalp, and allowed to buildup, scalp conditions become unfavorable and problems with scalp dryness and hair growth can arise.
Heavy oily concoctions inhibit optimal functioning of the scalp by clogging the pores and creating unhealthy environment for hair growth. This blockage can lead to scalp dryness, itchiness, inflammation and miniaturization (shrinking) of the hair follicles, and decrease in quality of the hair that emerges from the clogged follicles.
The proper way to hydrate the scalp and stimulate natural sebum production is simply through frequent cleansing and conditioning of the scalp.
For those who must supplement their scalp oils due to low natural sebum production, a moderate application of a sebum mimicking oil such as jojoba or a light plant based oil should do the trick.