The two basic requirements for a healthy scalp are cleanliness and _______?

For a healthy scalp, cleanliness is paramount, as it helps prevent the buildup of oils, dirt, and product residues that can lead to various scalp conditions and affect hair health. Stimulation is critical as well; it promotes blood circulation to the scalp. This increased blood flow delivers essential nutrients and oxygen to the hair follicles, which can help stimulate hair growth and improve the overall health of the scalp.

While moisture, nutrition, and protection are also important factors for maintaining healthy hair and scalp, they do not directly relate to enhancing scalp health in the same fundamental way that stimulation does. Moisture helps prevent dryness and itching, nutrition supports hair growth from within, and protection involves shielding the scalp from environmental damage, but stimulation specifically targets the blood flow that nourishes the scalp and hair follicles effectively.