1. Water (H₂O)
* Function: The most common solvent, acts as a diluent, carrier, and humectant.
* Characteristics: Polar, colorless, odorless, and readily available.
2. Alcohols
* Examples: Ethanol, Isopropyl Alcohol, Cetearyl Alcohol, Stearyl Alcohol
* Function:
* Ethanol: Used as a preservative, antimicrobial, and to improve product texture.
* Isopropyl Alcohol: Frequently used in toners and astringents for its drying properties.
* Cetearyl Alcohol & Stearyl Alcohol: Fatty alcohols that act as emollients (softening agents) and thickeners.
* Characteristics: Can be drying, but fatty alcohols are more moisturizing.
3. Glycols
* Examples: Propylene Glycol, Butylene Glycol
* Function: Humectants, solvents, and viscosity modifiers.
* Characteristics: Help retain moisture and improve texture.
4. Esters
* Examples: Isopropyl Myristate, Ethylhexyl Palmitate, Dimethicone
* Function: Emollients, provide a smooth feel, and help ingredients blend.
* Characteristics: Often have a silky texture, can be comedogenic (pore-clogging) depending on the specific ester.
5. Oils
* Examples: Mineral Oil, Coconut Oil, Castor Oil, Jojoba Oil
* Function: Emollients, moisturizers, and provide a barrier to prevent moisture loss.
* Characteristics: Vary widely in their properties; some are occlusive (form a barrier), while others are more easily absorbed.
6. Other Solvents
* Dimethicone: A silicone that acts as a solvent, emollient, and anti-foaming agent.
* PEG (Polyethylene Glycol): Used as a solvent, humectant, and viscosity modifier.
Important Considerations:
* Solvent Selection: The choice of solvent depends on the specific product, its intended use, and the desired properties.
* Safety: While generally safe in cosmetics, some solvents can cause irritation or allergic reactions. Always read product labels and check for any potential sensitivities.
Note: The specific solvents used in cosmetics can vary widely based on the product's formula, purpose, and brand.