Beta Hydroxy Acids (BHAs) are organic compounds which contain a carboxylic acid functional group and hydroxy functional group separated by two carbon atoms. They are closely related to alpha hydroxy acids, in which the two functional groups are separated by one carbon atom. Just like alpha hydroxy acids, beta hydroxy acids are simple organic acids found in nature or synthesized in the laboratory. Natural beta hydroxy acids, just like natural alpha hydroxy acids, are up to four times more gentle on the skin than their synthetic versions and thus are always preferred over synthetic acids in skincare formulations.
The main difference between alpha hydroxy acids and beta hydroxy acid as far as function is their lipid (oil) solubility. Alpha hydroxy acids are water soluble only, while beta hydroxy acids are soluble in oils (and alcohol). This means that beta hydroxy acids are able to penetrate into the oil-producing skin pores and exfoliate the dead skin cells that are built up inside the pore better than alpha hydroxy acids. Because of this difference in properties, beta hydroxy acids are better used on oily skin with blackheads, whiteheads, and general acne conditions.
Although beta hydroxy acids are now often portrayed as the latest skincare breakthrough, they have been around for quite a while. The most notable beta hydroxy acid, salicylic acid, has been used for treating acne for decades. In fact, acne treatment remains the use of choice for beta hydroxy acids as they are clearly superior to alpha hydroxy acids for this purpose. However, as far as skin exfoliation or reducing wrinkles, beta hydroxy acids are roughly on par with alpha hydroxy acids in that they complete the spectrum of hydroxy acid actions in a formula by extending the resurfacing benefits deeper into pores where alpha hydroxy acids penetrate less easily.
A Fuller Spectrum of Resurfacing With Beta Hydroxy Acids
By far the most popular beta hydroxy acid is Salicylic Acid that can be obtained from the bark of the Willow Tree (in fact the name is derived from the Latin word for Willow Tree, Salix). In plants it functions as a phenolic phytohormone that is used in the plant's growth/development, photosynthesis, and ion uptake/transport. In medicine its use dates back thousands of years, from the Greek physician Hippocrates who wrote in the 5th century BC about a bitter extract from Willow Tree Bark that could ease aches, pains, and fevers (this is because it is chemically very similar to aspirin). Many Native American tribes also used an infusion of the bark in their traditional medicine. Interesting, the active extract of willow bark, called salicin, supplies high levels of salicylic acid in a water soluble form (because it has not been separated and isolated from the entire extract into a powder). This makes naturally derived salicylic acid from willow bark one of the most preferred forms for use in skincare because it doesn't need alcohol or oil to make it soluble in the delivery medium, so the standardized extract can be incorporated into aqueous serums easily. This creates a more stable product that isn’t drying to the skin and that can penetrate deeper since aqueous serums are an ideal medium for delivery of active ingredients.
Ensuring Hydroxy Acid Formula Effectiveness
It is important to note that in addition to the concentration of hydroxy acids in products there are other factors that contribute or detract from their effectiveness. One of the most important factors in the effectiveness of hydroxy acid containing products is the pH level of the formula. An ideal pH is 3.5 to 4.0 (any lower and the product may be too acidic while any higher and the product's exfoliating benefits may be nullified). In the case of the undereye area, more is not always better. This fragile skin region is very sensitive and hydroxy acids should be used in low concentrations (the face is very forgiving of aggressive treatments, while the undereye area is not). Those using Retin-A, Renova, Accutane, or anything else that already has exfoliating or skin compromising actions should not use hydroxy acid products unless your physician has recommended that you do so. Even though at appropriate concentrations hydroxy acids should not overly increase sun sensitivity, using a product containing sunscreen during the day to protect the skin from UV exposure is recommended (which is beneficial even when not using hydroxy acids).