Potassium Hydroxide
- CAS
- 1310-58-3
- PubChem CID
- 14797
- Molecular Formula
- HKO
- Molecular Weight
- 56.1060 g/mol
A strong alkali. Can irritate the skin and eyes at high concentrations and may have a caustic effect.
What does it do?
A strong alkali that helps balance the pH of the formula; also used in soap making.
Details
Potassium hydroxide is a strong alkali (base) used to balance the formula's pH and in soap making. It is safe at low concentrations, but at high concentrations, it can irritate the skin and eyes or even cause caustic burns. EU regulations impose specific concentration limits on its use, and it is regulated under similar conditions as sodium hydroxide as a pH adjuster.
Hazards
Benefits
Functions
Restrictions
Where is it found?
Function & Use
Buffering
Skin-Conditioning Agent
Regulatory note
- EU 1223/2009 Annex IIIRestricted
Industry GHS notices (PubChem)
These are industry self-reports to ECHA, not our regulatory assessment.
- H290(20.9%)- H290
- H301- Toxic if swallowed
- H302(96.1%)- Harmful if swallowed
- H304- May be fatal if swallowed and enters airways
- H314(99.4%)- Causes severe skin burns and eye damage
- H318(24.7%)- Causes serious eye damage
- H370- Causes damage to organs
- H402- Harmful to aquatic life
What The Sources Say
CIR (Cosmetic Ingredient Review)2
Definition Inorganic hydroxides are alkaline salts formed by treating oxides with water or via decomposing salts by adding other soluble hydroxides to a solution thereof (e.g., adding sodium hydroxide to magnesium sulfate will produce magnesium hydroxide). The formation of an inorganic hydroxide, such as specifically lime or calcium hydroxide, by reaction of an oxide with water is a known as slaking.7 The resulting highly water soluble ingredients only vary structurally by the metal cation. These variations result in different degrees of alkalinity across these four ingredients, ranging in pK b values from 0.2 to 4.0. Used primarily as pH adjusters (to increase the pH of an otherwise acidic formulation), the caustic nature of these ingredients is unlikely to be observable in typical, final cosmetic formulations. Figure 1. Inorganic Hydroxides (wherein “M” is group I or II metal) The definitions, structures, and functions of the inorganic hydroxides included in this report are provided in Table 1. Chemical and Physical Properties The inorganic hydroxides are all highly water soluble, white solids with specific gravities around 2. Physical and chemical properties of the inorganic hydroxides in this report are provided in Table 2. Method of Manufacturing Calcium Hydroxide Calcium hydroxide may be formed by the hydration of lime or treating an aqueous solution of a calcium salt with alkali.8 Magnesium Hydroxide Magnesium hydroxide may be formed by reacting magnesium chloride or sulfate and sodium hydroxide.8 Most commercial-grade magnesium hydroxide is obtained from seawater or brine using lime or dolomitic lime.7 Potassium Hydroxide Potassium hydroxide may be produced by treating oxides with water, known as brine electrolysis.7,8 Sodium Hydroxide … [kırpıldı — bölüm toplam 9385 karakter]
Definition Inorganic hydroxides are alkaline salts formed by treating oxides with water or via decomposing salts by adding other soluble hydroxides to a solution thereof (e.g., adding sodium hydroxide to magnesium sulfate will produce magnesium hydroxide). The formation of an inorganic hydroxide, such as specifically lime or calcium hydroxide, by reaction of an oxide with water is known as slaking.11 The resulting highly water soluble ingredients only vary structurally by the metal cation. These variations result in different degrees of basicity across these four ingredients, ranging in pK b values from 0.2 to 4.0. Used primarily as pH adjusters (to increase the pH of an otherwise acidic formulation), the caustic nature of these ingredients is unlikely to be observable in typical, final cosmetic formulations, except when used in depilatory or hair straightener product types. Figure 1. Inorganic Hydroxides (wherein “M” is group I or II metal) The definitions, structures, and functions of the inorganic hydroxides included in this report are provided in Table 1. Chemical and Physical Properties The inorganic hydroxides are all highly water-soluble, white solids with specific gravities around 2. Physical and chemical properties of the inorganic hydroxides in this report are provided in Table 2. Method of Manufacturing Calcium Hydroxide Calcium hydroxide may be formed by the hydration of lime or by treating an aqueous solution of a calcium salt with alkali.12 Magnesium Hydroxide Magnesium hydroxide may be formed by reacting magnesium chloride or sulfate with sodium hydroxide.12 Most commercial-grade magnesium hydroxide is obtained from seawater or brine using lime or dolomitic lime.11 Distributed for comment only -- do not cite or quote Potassium Hydroxide … [kırpıldı — bölüm toplam 9506 karakter]
ToxValDB (EPA Toxicity Value Database)14
EPA ToxValDB skin/eye data — endpoint: Skin Irritation, classification: Skin corrosion/irritation - Category 1. Caveat: this is an aggregated record; dose, species and route of exposure must be considered together.
EPA ToxValDB skin/eye data — endpoint: Eye Irritation, classification: Category 1. Caveat: this is an aggregated record; dose, species and route of exposure must be considered together.
EPA ToxValDB skin/eye data — endpoint: Skin Sensitization, classification: Classification not possible. Caveat: this is an aggregated record; dose, species and route of exposure must be considered together.
EPA ToxValDB skin/eye data — endpoint: Eye Irritation, classification: Category 6.4A (Category 2A). Caveat: this is an aggregated record; dose, species and route of exposure must be considered together.
EPA ToxValDB skin/eye data — endpoint: Skin Irritation, classification: Category 6.3A (Category 2). Caveat: this is an aggregated record; dose, species and route of exposure must be considered together.
+9 more records.
Scientific References
- CIR — Safety Assessment of Inorganic HydroxidesCosmetic Ingredient Review (CIR), Personal Care Products Council(2014)
- EPA CompTox Chemicals Dashboard — DSSTox identifiers mapped to CAS (2021r1)US EPA, Center for Computational Toxicology and Exposure
- EU CosIng — Cosmetic Ingredient Database full exportEuropean Commission, DG GROW
- INCIDB — Skincare & Cosmetics INCI Database (Kaggle 2026.07)INCIDB (derived from EU CosIng, US FDA MoCRA, NLM DailyMed, OBF)
- OpenFDA Cosmetic Adverse Events (api.fda.gov/cosmetic/event)US FDA — unvalidated adverse event reports
- ToxValDB — genotoxicityUS EPA — ToxValDB v97
- ToxValDB — skin/eyeUS EPA — ToxValDB v97