What Is Aluminum Sesquichlorohydrate?
Aluminum sesquichlorohydrate is a form of aluminum chloride hydroxide with the formula Al4Cl3(OH)9. It belongs to a family of aluminum salts that can bind to water and proteins on the skin. These salts have been studied since the early 1900s when chemists noticed their ability to curb sweat and tighten skin. Over time formulators refined the compound into the balanced “sesquichloro” version that offers strong results with less skin irritation than older, harsher aluminum chlorides.
To make it, manufacturers combine aluminum chloride with aluminum hydroxide in water, then adjust the pH and temperature until the desired ratio of chloride to hydroxide forms. The mixture is filtered, dried and milled into a fine powder that dissolves easily in water or alcohol based formulas.
You will most often see aluminum sesquichlorohydrate in roll-on or stick antiperspirants, spray deodorants and cream or gel underarm products. It can also appear in foot sprays, body lotions aimed at reducing perspiration, facial toners that promise a pore tightening effect and certain wipe or pad treatments designed for quick freshening.
Aluminum Sesquichlorohydrate’s Cosmetic Benefits/Uses
This ingredient plays a few key roles in personal care products.
- Antiperspirant – Forms temporary plugs within sweat glands which slow down the flow of sweat to the skin surface, helping keep underarms or other areas drier for several hours
- Astringent – Contracts skin proteins for a firmer feel that can reduce the look of enlarged pores and give a smoother finish, useful in toners or post shave solutions
- Deodorant – Limits the amount of moisture and alters the environment on the skin so odor-causing bacteria have less chance to grow, resulting in fresher smelling skin
Who Can Use Aluminum Sesquichlorohydrate
This ingredient works best for people with normal, combination or oily skin that deals with noticeable perspiration. Dry or sensitive skin can still use it in low strengths but may feel tightness or a mild sting due to the salt content and slightly acidic pH. Those with eczema, broken skin or freshly shaved areas should be cautious because irritation is more likely when the skin barrier is already compromised.
Aluminum sesquichlorohydrate is a mineral-based compound produced synthetically, so it is generally suitable for vegans and vegetarians. Check the full product label though, as some formulas add waxes, fragrance or other ingredients sourced from animals.
Current safety reviews show that only a tiny amount of aluminum from topical antiperspirants is absorbed through intact skin. Most health authorities regard it as safe for use during pregnancy and breastfeeding. This is not medical advice and women who are pregnant or nursing should review any personal care product with their health professional to be sure it fits their individual situation.
The ingredient does not make skin more sensitive to sunlight, so it will not raise the risk of sunburn or require special daytime precautions beyond normal sunscreen use. It is also fragrance free by itself and does not interfere with most active skincare agents, making it easy to slot into a routine when extra sweat control is needed.
Potential Side Effects/Adverse Reactions
Responses to aluminum sesquichlorohydrate vary from person to person. The effects below are simply possibilities and most people will not notice any problem when using a well-formulated product.
- Temporary stinging or burning, especially on freshly shaved or broken skin
- Redness or mild irritation in users with sensitive or very dry skin
- Itching that subsides after the product is washed off
- Contact dermatitis marked by rash or swelling in rare cases of allergy
- Clogged pores or folliculitis if the sweat duct plug traps bacteria under heavy occlusion
- Yellow or white stains on fabrics when the ingredient mixes with sweat and detergents
If any unwanted reaction occurs stop using the product and seek advice from a healthcare professional.
Comedogenic Rating
Rating: 1 out of 5. Aluminum sesquichlorohydrate is water soluble and does not leave an oily residue that normally fuels blackheads. Its sweat-duct plugs form within the gland rather than coating the pore surface, so true pore blockage is uncommon. Occasional folliculitis can happen if bacteria get trapped under heavy use, which keeps the rating slightly above zero. Overall it is generally suitable for acne-prone or breakout-prone skin.
Because it is a salt that easily rinses away, build-up on the skin is minimal. Formulas that pair it with thick waxes or occlusive silicones can raise the likelihood of breakouts, so texture matters more than the active itself.
Summary
Aluminum sesquichlorohydrate acts as an antiperspirant, astringent and deodorant by reacting with sweat proteins to form temporary plugs, tightening skin proteins for a firmer feel and lowering moisture that bacteria rely on. Its effectiveness has kept it a staple in mainstream underarm products for decades, though newer “natural” options have drawn some users away.
Safety reviews show that only trace amounts penetrate intact skin and most people tolerate it well when used as directed. Still, individual sensitivities exist, so it is smart to patch test any new deodorant or toner that features this ingredient.