What pH level is likely to dry the skin?

A pH level of 3 is considered acidic, and products with such low pH levels can be overly harsh on the skin, leading to dryness and irritation. The skin's natural pH is slightly acidic, typically ranging from 4.5 to 5.5, which helps to maintain its barrier function and provides protection against pathogens. When the pH of a product drops to 3, it disrupts the skin's barrier, causing moisture to evaporate and leading to a dry, tight feel.

On the other hand, a pH level of 7 is neutral and usually does not dry the skin out. Meanwhile, a pH of 1 is very acidic, and while it may be effective for certain specific purposes, it is generally too harsh for use on skin. A pH level of 9 is alkaline and could also lead to dryness over time but is not as immediately detrimental as a pH of 3. Thus, level 3 is the most likely option to dry out the skin significantly.