Calcium Hydroxide is commonly referred to as slaked lime, is an essential inorganic compound utilized across numerous industries, including cosmetics. In cosmetic formulations, it functions as a pH adjuster, stabilizing the acidity of products and enhancing the activity of certain components. Its antimicrobial properties also contribute to product preservation. By supporting the stability and efficacy of cosmetic products, Calcium Hydroxide plays a crucial role in improving skin appearance and texture.
CAS Number: 1305-62-0
Molecular Formula: CaH2O2
Synonyms:
- Slaked lime
- Hydrated lime
- Lime hydrate
- Lime water
- Hydralime
- Lime milk
+ 19 more…
- Calcarea caustica
- Calcium hydroxide (Ca(OH)2)
- calcium(II) hydroxide
- Kalziumhydroxid
- Loeschkalk
- Carboxide
- geloeschter Kalk
- Ca(OH)2
- INS NO.526
- CHEBI:31341
- calcium(2+) hydroxide
- PF5DZW74VN
- E-526
- Hydroxide, Calcium
- O2 Patch
- KO2, Ca(OH)2
- CHEMBL2106388
- DTXCID5014410
- CHEBI:35150
Properties of Calcium Hydroxide
Chemical Identifiers
| EC Number | 215-137-3 |
| UNII | PF5DZW74VN |
| InChIKey | AXCZMVOFGPJBDE-UHFFFAOYSA-L |
| SMILES | [OH-].[OH-].[Ca+2] |
| IUPAC Name | calcium;dihydroxide |
| InChI | InChI=1S/Ca.2H2O/h;2*1H2/q+2;;/p-2 |
Physical and Chemical Properties
Calcium Hydroxide is a white, odorless solid, often in granular form. It exhibits high alkalinity, with a pH greater than 12 in aqueous solutions. While not highly soluble in water, it forms a suspension known as lime water. It reacts readily with acids, producing calcium salts and water. Hygroscopic in nature, it absorbs moisture from the environment. These properties make it versatile for use in applications ranging from cosmetics to construction and water treatment.
| Property | Value |
| pH | 12.4 (aqueous solution saturated at 25°C) |
| Odor | Odorless |
| Taste | Slightly bitter alkaline taste |
| Density | 2.24 at 68°F (USCG, 1999) – Denser than water; will sink |
| Color/Form | Crystals or soft granules or powder |
| Solubility | 0.2% at 32°F (NIOSH, 2024) |
| Flash Point | Non flammable |
| Boiling Point | 580°C |
| Melting Point | 1076°F |
| Refractive Index | 1.574 (alpha), 1.545 (beta) |
| Stability/Shelf Life | Readily absorbs carbon dioxide from air forming calcium carbonate |
| Other Experimental Properties | Loses water when ignited to form calcium oxide; forms CaO |
Structural Properties
Calcium Hydroxide is a simple compound with a small and basic structure, consisting of three heavy atoms. It has a molecular weight of around 74 grams per mole and does not contain isotopes or rotatable bonds. The compound is stable and can form hydrogen bonds, with two hydrogen bond donors and acceptors.
Its structure is canonical, meaning it follows a standard form for its chemical structure. It has a low polar surface area and no defined stereocenters, making it straightforward in terms of its geometric configuration. Overall, the compound is small, stable, and relatively simple in structure.
| Property | Value |
| Complexity | 0 |
| Exact Mass | 73.9680702 g/mol |
| Formal Charge | 0 |
| Heavy Atom Count | 3 |
| Molecular Weight | 74.09 g/mol |
| Monoisotopic Mass | 73.9680702 g/mol |
| Isotope Atom Count | 0 |
| Rotatable Bond Count | 0 |
| Compound Is Canonicalized | Yes |
| Hydrogen Bond Donor Count | 2 |
| Hydrogen Bond Acceptor Count | 2 |
| Covalently-Bonded Unit Count | 3 |
| Topological Polar Surface Area | 2 Ų |
| Defined Atom Stereocenter Count | 0 |
| Defined Bond Stereocenter Count | 0 |
| Undefined Atom Stereocenter Count | 0 |
| Undefined Bond Stereocenter Count | 0 |
Uses of Calcium Hydroxide in Cosmetics
Functional role in cosmetics:
- Calcium Hydroxide is used as a pH-regulating, hair processing, and mild antimicrobial agent in cosmetics.
Other uses:
- Calcium Hydroxide is used as a solid separation agent.
- It is also classified under the EPA Safer Chemical Functional Use Classes, primarily used as processing aids and additives.
Cosmetic Products Containing Calcium Hydroxide
Recent products using Calcium Hydroxide in their cosmetic formulations
- NOLEO 3-in-1 Diaper Care
- La Petite Creme Organic Diapering Lotion
- Mustela Liniment
- ORS Olive Oil Built-In Protection No-Lye Hair Relaxer Base
- Proclaim Argan Oil No-Lye Sensitive Scalp Relaxer System
- Nair Nourish Skin Renewal Hair Remover Cream for Face
- Glee the Body Hair Removal Cream
- Brylcreem 3 in 1 Hair Cream
- Magic Fragrant Shaving Powder (Gold) for All Skin Types
Top companies using Calcium Hydroxide in their cosmetic products
- NOLEO
- La Petite Creme
- Mustela
- ORS Olive Oil
- Proclaim
- Nair
- Glee the Body
- Brylcreem
- Magic
How Calcium Hydroxide Works in Formulations
Calcium Hydroxide is used in cosmetics primarily as a pH adjuster and buffering agent. It helps to control the acidity or alkalinity of formulations, making it useful in products like hair relaxers, depilatories, and some skincare products.
Ideal Concentration and Benefits in Different Formulations
pH Adjuster and Buffering Agent
Calcium Hydroxide is commonly used to raise the pH of formulations, particularly when an alkaline environment is needed for product efficacy.
- Concentration: 0.1%–5%
- Benefit: It is particularly useful in formulations where a high pH is necessary, such as in hair care products like relaxers and depilatories.
Chemical Reactivity
As a strong alkaline substance, Calcium Hydroxide reacts with acidic ingredients in formulations. It is important to ensure proper pH balance when combining Calcium Hydroxide with other active ingredients. In some cases, Calcium Hydroxide may also react with certain oils or waxes, so its compatibility should be tested in formulations that include these ingredients.
Stabilizer for Active Ingredients
Calcium Hydroxide is sometimes used to stabilize other ingredients in formulations, such as pigments, and to prevent degradation in products. It can be used to enhance the stability of certain actives in products by providing an optimal pH environment for their performance.
Compatibility with Other Ingredients
Calcium Hydroxide is compatible with most emulsifiers and surfactants, but care should be taken when formulating with highly acidic ingredients, which could lead to the neutralization of the ingredient. It can interact with citric acid, ascorbic acid, or other ingredients requiring acidic pH levels, leading to neutralization or altered effectiveness.
Stability and Shelf Life
Calcium Hydroxide is stable when stored in airtight containers to prevent absorption of moisture, which can reduce its effectiveness or cause it to react with other ingredients in the formulation.
- Shelf life: 2–3 years
- Best storage: Keep in a dry, cool place in airtight containers to prevent moisture absorption, which could compromise its effectiveness
Formulation Challenges and Troubleshooting
While Calcium Hydroxide is effective in cosmetics, there are some formulation challenges to consider:
pH Sensitivity
Calcium Hydroxide is a strong alkaline substance, and its high pH can disrupt formulations if not properly controlled.
Solution: Carefully monitor the pH of the formulation to ensure it stays within the desired range (typically 4.5–7 for most cosmetic products). Use pH buffers, such as citric acid, to stabilize the pH and prevent over-adjustment.
Reactivity with Acids
Calcium Hydroxide reacts with acids and may neutralize them, potentially affecting the formulation’s performance.
Solution: Test compatibility with acidic ingredients before large-scale production. Adjust the ratio of Calcium Hydroxide and acid components to prevent neutralization and maintain the intended product functionality.
Irritation and Skin Sensitivity
While Calcium Hydroxide is safe in small quantities, high concentrations or prolonged exposure can cause irritation, especially for sensitive skin.
Solution: Use Calcium Hydroxide in low concentrations (typically below 2%) and conduct patch testing on sensitive skin formulations. Avoid excessive use in leave-on products like creams or lotions.
Stability of Active Ingredients
Calcium Hydroxide can affect the stability of other active ingredients, especially those sensitive to changes in pH.
Solution: Ensure that the formulation is balanced with compatible ingredients and monitor the stability of the product over time. Consider using stabilizers or alternative pH-adjusting agents if necessary.
Packaging Compatibility
Calcium Hydroxide can react with certain packaging materials, especially those sensitive to high pH levels.
Solution: Use packaging materials that are resistant to high pH, such as glass or certain plastics like polyethylene or polypropylene, to prevent degradation of the packaging and ensure product safety.
Is Calcium Hydroxide Safe in Cosmetics?
Safety reports for Calcium Hydroxide are given below:
- Safety Assessment of Inorganic Hydroxides as Used in Cosmetics. Download PDF
Regulatory Considerations for Using Calcium Hydroxide in Cosmetic Formulations
Few regulatory considerations are to be taken into account before using Calcium Hydroxide as an ingredient. Given below is the list of those regulations:
FDA Requirements: Over-the-counter (OTC) drug products containing certain active ingredients are marketed for various uses. However, there is insufficient evidence to establish the safety and effectiveness of some ingredients for these uses. Calcium Hydroxide is included in antidiarrheal drug products under this category.
FIFRA Requirements: In compliance with FIFRA, the EPA conducts a comprehensive evaluation of older pesticides to assess their health and environmental impacts and determine their suitability under updated safety standards such as those in the Food Quality Protection Act of 1996. Pesticides are categorized by their potential human exposure and associated risks. Calcium Hydroxide is included in List D, indicating lower priority. Case No: 4066; Pesticide type: Fungicide, Herbicide, Antimicrobial; Case Status: The active ingredient is no longer supported for reregistration and is categorized as unsupported or cancelled. Active ingredient (AI): Calcium Hydroxide; AI Status: No longer present in any registered pesticide products.
New Zealand EPA Inventory of Chemical Status: Calcium Hydroxide does not hold an individual approval but is permissible under appropriate group standards.
Calcium Hydroxide Side Effects
Calcium Hydroxide, or slaked lime, is a corrosive substance known for its potential to cause severe skin, eye, and respiratory damage. Eye exposure can result in intense irritation and burns, while skin contact may lead to blisters and dermatitis. Inhalation of its dust can irritate the respiratory tract and, in extreme cases, cause pulmonary complications.
Ingestion poses a significant risk, potentially causing gastrointestinal burns and severe discomfort. Proper handling practices, including personal protective equipment, are critical to prevent adverse effects during use.
Symptoms
- Eye Exposure: Causes redness, pain, and severe burns.
- Skin Exposure: Leads to redness, roughness, dryness, pain, skin burns, and blistering.
- Ingestion Exposure: Results in burning sensations, abdominal pain, cramps, and vomiting.
- Inhalation Exposure: May cause sore throat, coughing, and a burning sensation.
Target Organs
Primarily affects the eyes, skin, and respiratory system.
Adverse Effects
Calcium Hydroxide is a dermatotoxin, leading to skin burns and irritation.
Exposure Routes
Absorption occurs through inhalation of aerosols and ingestion.
Non-Human Toxicity Values
The LD50 (Lethal Dose, 50%) of Calcium Hydroxide is 7.3 g/kg (range: 4.8–11.1 g/kg) when administered orally to rats. This indicates the dose lethal to 50% of the test population, with variability based on individual susceptibility.
Antidote and Emergency Treatment
- Immediate First Aid: Remove the patient from exposure immediately. Ensure thorough decontamination. For non-breathing patients, administer artificial respiration using a resuscitator or bag-valve-mask device. Perform CPR if required. Flush contaminated eyes with water continuously. Avoid inducing vomiting; position the patient to maintain an open airway if vomiting occurs. Seek medical attention promptly and maintain normal body temperature.
- Basic Treatment: Establish a clear airway (oropharyngeal or nasopharyngeal airway if necessary). Provide suction when required. Administer oxygen via nonrebreather mask at 6–12 L/min. Monitor and manage pulmonary edema and shock. For eye exposure, irrigate with saline (0.9% NS) during transport. Avoid emetics for ingestion. Dilute with water (5 mL/kg up to 200 mL) if the patient can swallow. Do not neutralize with acids. After decontamination, cover burns with sterile dressings.
- Advanced Treatment: For severe respiratory distress or unconscious patients, intubation may be required. Positive-pressure ventilation can be beneficial. Administer fluids cautiously to manage hypotension while avoiding fluid overload. Treat arrhythmias and monitor cardiac rhythm. Use proparacaine hydrochloride to assist with eye irrigation if necessary.
Environmental and Sustainability Impact
Calcium Hydroxide, commonly known as slaked lime, is used in cosmetics for its pH-adjusting properties. While it provides functional benefits, its environmental impact must be carefully considered:
Environmental Impact
- Water Pollution: Calcium Hydroxide is alkaline and can increase the pH of water bodies if released in large quantities, which can be harmful to aquatic organisms. It can also lead to sedimentation when added to water, potentially affecting water quality and ecosystem balance.
- Carbon Footprint: The production of Calcium Hydroxide involves the conversion of calcium carbonate (lime) in a high-temperature kiln, which is energy-intensive and can produce CO₂ emissions. The carbon footprint depends largely on the energy source used during production.
Sustainability
The sustainability of Calcium Hydroxide is influenced by its production and disposal practices.
- Raw Materials: Calcium Hydroxide is derived from naturally abundant limestone, which is relatively sustainable, but its production process can be energy-intensive and generate carbon emissions.
- Energy Use: The process of converting limestone to Calcium Hydroxide requires significant energy, typically from fossil fuels, though it could be made more sustainable by using renewable energy sources.
- End-of-Life Impact: Once used in formulations, Calcium Hydroxide can break down into calcium carbonate, which is naturally occurring and harmless. However, if improperly disposed of in large quantities, it can contribute to local pH imbalances in water bodies.
Biodegradability and Toxicity
Calcium Hydroxide is not toxic to humans at the concentrations typically used in cosmetics and is considered safe for topical use. It is also biodegradable, breaking down into calcium carbonate over time.
- Toxicity: In large quantities, Calcium Hydroxide can be harmful to aquatic life due to its ability to raise pH levels. However, its environmental toxicity is generally low when used properly in small amounts in formulations.
- Environmental Impact: Calcium Hydroxide poses minimal long-term environmental impact in most cosmetic applications, provided proper disposal guidelines are followed to prevent significant release into water bodies.
Eco-Friendly Alternatives
There are alternatives to Calcium Hydroxide that may offer lower environmental impact in some formulations:
- Sodium Bicarbonate: A milder and more eco-friendly alternative to Calcium Hydroxide, sodium bicarbonate can be used in many formulations requiring pH control.
- Potassium Hydroxide: Another alkaline alternative, potassium hydroxide is sometimes considered more effective in liquid formulations and is biodegradable.
- Magnesium Hydroxide: A gentler, eco-friendly alkaline ingredient used in deodorants and skincare.
- Arginine: A natural amino acid with mild alkalizing properties, suitable for gentler pH adjustments.
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