Difference Between Alpha and Beta Hydroxy Acids

Main Difference – Alpha vs Beta Hydroxy Acids

Alpha and beta hydroxy acids are organic compounds that are mainly used in cosmetic productions. Both these compounds are used in these products due to their ability to exfoliate the skin or to remove the dead cell layers of skin. Alpha hydroxy acids are commonly used than beta hydroxy acids. The main difference between alpha and beta hydroxy acids is that in alpha hydroxy acids, the hydroxyl group and carboxylic acid group are separated by one carbon atom whereas, in beta hydroxy acids, the hydroxyl group and carboxylic acid group are separated by two carbon atoms.

Key Areas Covered

1. What are Alpha Hydroxy Acids
     – Definition, Use in Skincare Products, Side Effects
2. What are Beta Hydroxy Acids
     – Definition, Use in Skincare Products
3. What is the Difference Between Alpha and Beta Hydroxy Acids
     – Comparison of Key Differences

Key Terms: Alpha Hydroxy Acids, Beta Hydroxy Acids, Carboxylic Acid Group, Hydroxyl Group, Skin Care Products

What are Alpha Hydroxy Acids

Alpha hydroxy acids are organic compounds containing a carboxylic acid group with a hydroxyl group (-OH) group attached to its adjacent carbon atom. This means there are two functional groups (a carboxylic group and a hydroxyl group) in alpha acids, located adjacent to each other.

There are naturally occurring alpha hydroxy acids as well as synthetic compounds. These compounds are well known for their use in cosmetic industry. The simplest alpha hydroxy acid is glycolic acid. It has applications in many industries such as food industry and textile industry. The most common alpha hydroxy acids are lactic acid and glycolic acid. The alpha hydroxy acids originate from milk and fruit sugars.

Figure 1: Chemical Structure of Lactic Acid

Alpha hydroxy acids are used in cosmetic industry due to its ability to reduce wrinkles and improve the look and feel of the skin. Human skin has two major cell layers: avascular epidermis and vascular epidermis. On the top of the skin, there is a thin layer (with a thickness of one or two cells) which is considered as a dead cell layer. The role of alpha hydroxy acids is to remove the “glue” from the upper layer of skin, allowing new cell layers to grow by removing dead cell layers. Therefore, alpha hydroxy acids are very helpful in removing wrinkles.

However, there are two major side effects of alpha hydroxy acids when used in skincare products. One is sensitivity to sunlight. Alpha hydroxy acids can increase this sensitivity by 50%. Irritation is the other major side effect. The symptoms may include redness, itching, etc.

What are Beta Hydroxy Acids

Beta hydroxy acids are organic compounds containing a carboxylic acid group and a hydroxyl group separated by two carbon atoms. Beta hydroxy acids are closely related to beta hydroxy acids; in alpha hydroxy acids, the hydroxyl group is separated from the carboxylic acid group by one carbon atom.

Figure 2: Salicylic Acid Chemical Structure

Beta hydroxy acids are less commonly used compared to alpha hydroxy acids. However, salicylic acid is a major beta hydroxy acid used in skin care products. Beta hydroxy acids are more oil soluble. Hence these are used for skincare products that are suitable for acne treatments for oily skin. Unlike alpha hydroxy acids, these beta hydroxy acids tend to cause less skin irritations.

Difference Between Alpha and Beta Hydroxy Acids

Definition

Alpha Hydroxy Acids: Alpha hydroxy acids are organic compounds containing a carboxylic acid group with a hydroxyl group (-OH) group attached to its adjacent carbon atom.

Beta Hydroxy Acids: Beta hydroxy acids are organic compounds containing a carboxylic acid group and a hydroxyl group separated by two carbon atoms.

Location of Functional Groups

Alpha Hydroxy Acids: In alpha hydroxy acids, carboxylic acid group and hydroxyl group are separated by one carbon atom.

Beta Hydroxy Acids: In beta hydroxy acids, carboxylic acid group and hydroxyl group are separated by two carbon atoms.

Solubility

Alpha Hydroxy Acids: Alpha hydroxy acids are less soluble in oil.

Beta Hydroxy Acids: Beta hydroxy acids are highly soluble in oil.

Uses

Alpha Hydroxy Acids: Alpha hydroxy acids are found in skincare products.

Beta Hydroxy Acids: Beta hydroxy acids are found in skincare products that are suitable for oily skins.

Abilities

Alpha Hydroxy Acids: Alpha hydroxy acids are capable of reducing wrinkles and improving the look and feel of the skin.

Beta Hydroxy Acids: Beta hydroxy acids are suitable for treatment of acne.

Side Effects

Alpha Hydroxy Acids: Alpha hydroxy acids increase the sensitivity to sunlight and cause skin irritations.

Beta Hydroxy Acids: Beta hydroxy acids cause fewer skin irritations than alpha acids.

Conclusion

Alpha and beta hydroxy acid are two organic compounds that contain a hydroxyl group and a carboxylic acid group in the same molecule. The main difference between alpha and beta hydroxy acids is that in alpha hydroxy acids, the hydroxyl group and carboxylic acid group are separated by one carbon atom whereas, in beta hydroxy acids, the hydroxyl group and carboxylic acid group are separated by two carbon atoms.

Reference:

1. “Alpha Hydroxy Acid (AHA).” Glycolic Acid, Available here.
2. “Beta hydroxy acid.” Wikipedia, Wikimedia Foundation, 6 July 2017, Available here.
3. Jones, Cindy. “Alpha & Beta Hydroxy Acids.” LIVESTRONG.COM, Leaf Group, 3 Oct. 2017, Available here.

Image Courtesy:

1. “Salicylic acid chemical structure” (CC BY-SA 3.0) via Commons Wikimedia
2. “Lactic-acid-skeletal” By NEUROtiker – Own work (Public Domain) via Commons Wikimedia