Sodium Hydroxide is also known as lye or caustic soda. It is used to adjust the pH of products; many ingredients require a specific pH to be effective.

In small amounts, sodium hydroxide is considered safe to use. However, large amounts may cause chemical burns due to its high alkaline.

This gentle cleansing and foaming ingredient is known for leaving a smooth feeling in skin and hair. It is made using coconut oil.

According to the manufacturer, it is soluble in water and has resistance to hard water, acid, and alkali.

Urea is also called carbamide and is the diamide of carbonic acid. In cosmetics, urea is used to hydrate the skin. It also provides exfoliation in higher concentrations.

As a humectant, urea helps draw moisture from the air and from deep within the skin. This helps hydrate your skin. Studies show urea is an effective moisturizer for dry skin conditions. 40% urea is typical in medications for treating eczema and other skin conditions.

Water. It's the most common cosmetic ingredient of all. You'll usually see it at the top of ingredient lists, meaning that it makes up the largest part of the product.

So why is it so popular? Water most often acts as a solvent - this means that it helps dissolve other ingredients into the formulation.