Final answer:
The pH level of skin, hair, and scalp falls within the slightly acidic range of 4-6 on the pH scale, which helps with protective barrier functions and moisture retention.
Step-by-step explanation:
The pH level of skin, hair, and scalp typically falls within the range of 4-6. This slightly acidic environment helps to maintain barrier function against bacterial infection and retains moisture. The pH scale, an inverse logarithm, ranges from 0 to 14. According to this scale, substances with a pH below 7, like the skin, are considered acidic. Substances with a pH above 7 are considered alkaline, and a pH of 7 is neutral, like pure water. Extreme pH levels in either direction generally are inhospitable to life. In humans, the blood maintains a slightly alkaline pH, usually around 7.4, which is tightly regulated through mechanisms including the bicarbonate system, as this homeostatic control is essential for many bodily functions.