Emollients are among the most common ingredients used in personal care formulations. The word emollient is derived from the Latin word mollis or molle, which means soft, pliable, and supple.

Emollients are normally defined as ingredients that impart a smooth, soft, or lubricious feeling to skin. The term emolliency usually refers to the spreading and lubricity on skin or hair as a function of time.

Benefits of emollients

Emollients, however, are multifunctional ingredients that can provide numerous other benefits such as;

• Modify skin feel: skin feel correlates closely with molecular weight (MW) and viscosity
• Provide shine to skin, hair, and lips: the refractive index of an emollient correlates well with skin shine
• Condition hair: mainly use high MW Silicone fluids (>100K cSt.)
• Act as the main formulation carrier in anhydrous formulations
• Act as an active solvent: generally high polarity emollients are preferred
• Thicken anhydrous, oil in water, and water in oil formulations
• Moisturize, skin, and improve skin elasticity
• Reduce skin moisture loss (transepidermal water loss, or TEWL)
• Modulate active skin delivery
• Can reduce the appearance of wrinkles
• Can increase cell turnover

Chemical types of emollients

The chemical types of emollients include esters (most common), fatty alcohols,  fatty acids, ethers, silicones, and hydrocarbons.

Esters are compounds formed by reacting acids with alcohols or polyols. Most natural emollients are triglyceride based oils formed by reacting Glycerin with fatty acids. Many esters however are not stable at low or high PH and can break down into their starting materials over time. In general, the more water soluble an ester is, the lower is its hydrolytic stability. Also, highly branched esters are more stable.

Fatty alcohols are organic compounds in which a hydroxyl group is attached to a saturated, unsaturated, or branched carbon and the chain length is greater than about seven carbons. Typical fatty alcohols used in formulations include Cetyl, Stearyl, Isostearyl, Oleyl, Octyldodecyl, and Behenyl alcohols.

Fatty acids are mono carboxylic acids having a chain length greater than about seven carbons. Typical fatty acids used include Lauric, Myristic, Palmitic, Stearic, Oleic, Isostearic, Ricinoleic, and Behenic acid.

Ethers are compounds in which an oxygen atom connected to two alkyl or aryl groups and are very stable to low or high PH and oxidizing agents.

Silicones are linear or cyclic polymers of silicone/oxygen monomers. The polymers are made up of alternating silicone and oxygen atoms and may carry end or pendant block groups that can be functionalized. Dimethicone (various MWs), Cyclopentasiloxane, and Dimethicone/ Dimethicone Crosspolymers are the types mainly used as emollients.

Hydrocarbons are compounds carrying only carbon and hydrogen groups. These include aliphatic, cyclic, and aromatic groups. The main types used include mineral oil, Petrolateum, Squalane, Isododecane, Isohexadecane, Microcrystalline wax, Polyethylene, Ozokerite, and Paraffin wax.

Factors to consider in choosing emollients

• The desired skin or hair benefit: my preference is to use emollients that are multifunctional.
• Skin compatibility, irritation profile: low MW emollients typically are more irritating than high MW ones.
• Polarity: important when solubilizing sunscreens like Avobenzone.
• Spreading characteristics: typically you need to use combinations of high, medium and low spreading emollients to get the right skin feel. Low MW/viscosity emollients rapidly spread on skin and have a less greasy, lighter feel.
• Substantivity: important for rinse off products. The structure, MW, and viscosity are the critical factors.
• Impact on foam/lather: important for shampoo and body wash formulations. You need to use emollients that have a high enough MW so they don’t readily form micelles.
• Stability: important for high or low PH formulations and those containing oxidizing or reducing agents.
• Concept support (when using exotic oils or butters)
• Global approval/availability
• Cost

Recommended products

Volatile emollients: used to provide temporary emolliency and aid in film formation.

• Cyclopentasiloxane (Xiameter PMX-0245 Cyclopentasiloxane-Nexeo Solutions)
• Isododecane (Permethyl 99-PreSperse)
• Dimethicone .65 cSt. (Xiameter PMX-200 Silicone Fluid, 65 cSt-Nexeo Solutions)
• Isoparaffin cuts (C9-C16)
• Ethyl Trisiloxane (Silsoft ETS Trisiloxane-Momentive Performance Chemicals)
• Caprylyl Methicone (Dow Corning FZ-3196)
• Trisiloxane (Xiameter PMX-200 Silicone Fluid 1 cSt-Nexeo Solutions)

Natural emollients

• Jojoba, Safflower, Coconut, Castor, Sunflower, Palm, Peanut, and Olive oil
• Coca and Shea butter
• Carnauba, Candellila, and Beeswax
• Squalane

Light skin feel, fast spreading emollients (MW<300 Daltons)

• Cyclopentasiloxane (Xiameter PMX-0245 Cyclopentasiloxane-Nexeo Solutions)
• Isopropyl Isostearate (Schercemol 318 Ester-Lubrizol)
• Hydrogenated Polyisobutene (Polyiso 200,250- Elementis)
• Propylheptyl Caprylate (Cetiol Soft-BASF)
• Dicaprylyl Carbonate (Cetiol CC-BASF)
• Dicaprylyl Ether (Cetiol OE-BASF)
• C12-15 Alkyl Lactate (Ceraphyl 41-Ashland)
• C12-15 Alcohol Benzoate (Finsolv TN-Innospec)

Medium skin feel, spreading emollients

• Diisopropyl Dimer Dilinoleate (Dermol DID-Alzo)
• Isostearyl Isostearate (Schercemol 1818 Ester)
• PPG 15 Stearyl Ether (Arlamol E-Croda)
• Caprylic/Capric Triglyceride (Myritol 312-BASF)
• Cetyl Ricinoleate (Naturechem CR-Vertellus Performance Materials)
• Neossance Squalane (Squalane-Centerchem)
• Hydrogenation Polyisobutene (Polyiso 300, 450- Fancor)
• Dimethicone (5-50 cSt)

Cushion Emollients: used to provide residual emolliency

• Pentaerythritol Tetraisostearate (Crodamol PTIS-Croda)
• Pentaerythritol Tetraoctanoate (Trivent PE-48-Alzo)
• Isocetyl Stearoyl Stearate (Ceraphyl 791-Ashland)

Emollients for solubilizing polar, crystalline actives

• Butylphthalimide Isopropylphthalimide (Pelemol PIP-Phoenix Chemical)
• Dipropylene Glycol Dibenzoate (Finsolv PG22-InnoSpec)
• Phenyl Ethyl Benzoate (Extend 226-Ashland)
• Diethyl Hexyl Maleate (Bernel Ester DOM-Alzo)
• Dicaprylyl Isosorbide (HydraSynol DOI-Sytheon)
• Isopropyl Lauroyl Sarcosinate (Eldew SL 205-Ajinomoto)
• Propylene Glycol Dibenzoate (LexFeel Shine-Inolex)

Hydrating/moisturizing emollients

• PPG 15 Stearyl Ether (Arlamol PS15E-Croda)
• Isopropyl Isostearate (Schercemol 318 Ester-Lubrizol)
• C12-15 Lactate (Ceraphyl 41 Ester-Ashland)
• Di-C12/13 Maleate (Cosmacol EMI-Sasol)

Emollients for increasing skin elasticity

• PPG 15 Stearyl Ether (Arlamol PS15E -Croda)
• Propylene Glycol Isostearate (Citrol PGIS -Croda)
• Trimethylolpropane Triisostearate (Crodamol TTIS-Croda)

Emollients for TEWL reduction

• Petrolatum
• Isostearyl Neopentanoate (Wickenol 150-Alzo)
• Isostearyl Isostearate (Dermol 1818-Alzo)
• Di-C12-13 Alkyl Malate (Cosmacol EMI -Sasol)
• Cosmacol ELI (C12/13 Lactate-Sasol)
• Squalane (Neossance Squalane-Centerchem)