Aluminum Sesquichlorohydrate (ASH) is a widely used ingredient in personal care products. This compound is an aluminum salt primarily utilized for its ability to manage perspiration. Regulatory bodies classify ASH as an active drug ingredient in over-the-counter antiperspirant formulations designed to control moisture and odor. Understanding ASH requires examining its chemical structure, its mechanism for controlling sweat, and its safety profile.
Defining Aluminum Sesquichlorohydrate
Aluminum Sesquichlorohydrate is an inorganic chemical compound that is a complex, polymeric form of basic aluminum chloride. The term “sesquichlorohydrate” refers to the specific ratio of aluminum to chloride in the compound’s molecular structure. Unlike simpler aluminum salts, ASH is not a single, fixed molecule but rather a range of polymeric complexes loosely bound to water molecules.
The aluminum-to-chloride atomic ratio in this compound ranges between approximately 1.26:1 and 1.90:1. This polymeric structure distinguishes it from other antiperspirant ingredients, such as aluminum chloride, which has a simpler, more acidic structure. ASH is a water-soluble, white to off-white powder, making it suitable for incorporation into various personal care formulations.
How it Functions as an Antiperspirant
The primary function of Aluminum Sesquichlorohydrate is to reduce the flow of sweat to the skin’s surface. When applied, the compound dissolves in the moisture found within the eccrine sweat ducts. The aluminum and chloride ions then precipitate and polymerize, forming a temporary, gelatinous plug inside the duct.
This blockage reduces the amount of perspiration reaching the skin, controlling wetness and odor. The effect is temporary and reversible; the plug is naturally shed over several days as the skin renews itself through desquamation. ASH is often preferred over compounds like aluminum chloride because its larger polymeric structure results in reduced acidity, making it less irritating and a gentler option for daily use.
Health Concerns and Safety Assessment
Concerns have been raised by consumers regarding the safety of aluminum compounds in antiperspirants, particularly unsubstantiated claims linking them to diseases such as breast cancer and Alzheimer’s disease. Current scientific literature and major regulatory bodies do not support these popular claims. The American Cancer Society, for instance, has concluded that there is no clear and consistent scientific evidence linking the use of aluminum-containing antiperspirants to an increased risk of breast cancer.
Research indicates that only a minute fraction of the aluminum applied in antiperspirants is actually absorbed through the skin, an amount significantly lower than the aluminum absorbed through normal dietary intake. The Food and Drug Administration (FDA) in the United States has reviewed the safety of aluminum salts, including Aluminum Sesquichlorohydrate, and permits its use in over-the-counter antiperspirants at concentrations up to 25%. The FDA requires a warning on antiperspirant labels advising individuals with kidney disease to consult a doctor before use. This is a precaution for those with severely compromised kidney function, as the kidneys are responsible for clearing aluminum from the body, but it poses no risk to the average person with healthy kidneys. Scientific consensus maintains that, based on current data, the compound is safe for its intended cosmetic use.