To some extent, yes. It's not necessarily true that the product must have exactly the same pH as skin (or hair). However, it is true that outside a certain pH range, the product may cause damage to skin or hair.
Alkali
No an alkali is the opposite of an acid. Alkali = basic; acid = acidic.
alkali is used to reduce acid and acid is used to reduce alkali
acids
alkali
All alkali metals and alkali earth metals below calcium react vigorously with acids.
Neither
i think acids
No. Alkali's and acids are an separate ends of the pH scale, the pH of acids being 1, 2, 3, 4 and 5 (strong to weak) and the pH of alkali's being 11, 12, 13, 14 and 15 (weak to strong). Examples of acids are hydrochloric acid (strong) and vinegar (weak). Toothpaste is an example of a weak alkali.
Magnesium oxide is a basic compound, also known as an alkali. It reacts with acids to form salts and water.
This substance is called a pH indicator.
Alkali's neutralise acids. For example, toothpaste is an alkali that neutralises acid in the mouth.