The one ingredient missing in Aveeno soap is soap. In fact, Aveeno calls its signature cleanser a moisturizing bar --- not a bar of soap. Instead of soap, Aveeno uses natural colloidal oatmeal as its key ingredient. The oatmeal is combined with a number of other ingredients to make a cleanser that also can help soothe irritated skin and help skin stay softer.

Oat Flour

The main ingredient in Aveeno's moisturizing bar is oat flour. Aveeno uses finely ground oats, known as colloidal oatmeal, which help to relieve itching and minor skin irritation. The Aveeno product is sometimes recommended for people who are suffering from rashes, eczema, insect bites or poison ivy. Aveeno claims that the oat proteins in the flour leave a protective barrier on the skin which can help the skin retain moisture.

Cetearyl Alcohol

Cetearyl alcohol is another major ingredient in the Aveeno bars. The Cosmetics Info website reports the ingredient is common in skin care products because it helps to keep the oil and liquid components in a product from separating. Manufacturers also include it to increase a product's foaming ability.

Stearic Acid and Sodium Cocoyl Isethionate

Stearic acid comes from animal and vegetable fats and oils and is used in many cosmetic creams, cakes, soaps and pastes. Cosmetics Info reports that stearic acid is used in soaps and cleansers because it works as a surfactant, which helps water mix with oil and dirt so you can wash them away. Sodium cocoyl isethionate is an ingredient that comes from coconut oil that also performs as a surfactant.

Moisturizers

Aveeno's Moisturizing Bar also contains a number of moisturizing ingredients. Glycerin helps to slow the loss of moisture from a product during use, according to Cosmetics Info. Hydrogenated vegetable oil and hydrogenated castor oil help to slow the loss of water from the skin by forming a barrier on the skin's surface.

Titanium Dioxide

Titanium dioxide is approved by the U.S. Food and Drug Administration as a color additive. You'll find it in a wide range of cosmetics and as a sunscreen agent in some personal care products.

Citric Acid

You might be familiar with citric acid as the acid found in fruits such as oranges and lemons. According to Cosmetics Info, manufacturers add it to aftershave lotions, baby shampoos and makeup because it provides a lemon-like fragrance.

Sodium Trideceth Sulfate

The Environmental Working Group's cosmetic safety database describes sodium trideceth sulfate as a commonly used cleansing agent and a foaming agent.