Shaving Formulations

Three main types of shaving preparations may be distinguished (1) Wet shaving formulations (2) dry shaving formulations and (3) after shave preparations. 

The most commonly used shaving formulations are those of the aerosol type, whereby hydrocarbon propellants (e.g. butane) are used to dispense the foam. The amount of propellant is critical for foam characteristics. More recently, several companies have introduced the concept of post-foaming gel, whereby the product is discharged in the form of a clear gel which can be easily spread on the face and the foam is then produced by vaporisation of low-boiling hydrocarbons such as iso-pentene. Due to the high viscosity of the gel, the latter is packed in a bag separated from the propellant used to expel the gel. 

Another important formulation that is used after shaving is that used to reduce skin irritation and provide a pleasant feel. This can be achieved by providing emol-liency accompanied by a cooling effect. In some cases an antiseptic agent is added to keep the skin free from bacterial infection. Most of these after-shave formulations are aqueous-based gels, which should be non-greasy and easy to rub into the skin. 

Quick-breaking foams consist of a miscible solvent system such ethanol (qv) [64-17-5] and water, and a surfactant that is soluble in one of the solvents but not in both. These foams are advantageous for topical appHcation of pharmaceuticals because, once the foam hits the affected area, the foam coUapses, deUvering the product to the wound without further injury from mechanical dispersion. This method is especially usehil for treatment of bums. Some personal products such as nail poHsh remover and after-shave lotion have also been formulated as quick-breaking foams. 

Emulsions of fatty- and petroleum-based substances, both oils and waxes, of the o/w type are made by using blends of sorbitan fatty esters and their poly(oxyethylene) derivatives. Mixtures of poly(oxyethylene(20)) sorbitan monostearate (Polysorbate 60) and sorbitan monostearate are typical examples of blends used for lotions and creams. Both sorbitan fatty acid esters and their poly(oxyethylene) derivatives are particularly advantageous in cosmetic uses because of their very low skin irritant properties. Sorbitan fatty ester emulsifiers for w/o emulsions of mineral oil are used in hair preparations of both the lotion and cream type. Poly(oxyethylene(20)) sorbitan monolaurate is useflil in shampoo formulations (see Hairpreparations). Poly(oxyethylene) sorbitan surfactants are also used for solubilization of essential oils in the preparation of colognes and after-shave lotions. 

After-Shaves. After-shave preparations serve the same function as and are formulated similarly to skin asttingents. After-shave balms are hydro-alcohoHc or alcohol-free emulsions that supply soothing iagredients, for example, witch ha2el, and em ollients, for example, decyl oleate [3687-46-5] to the skin. Menthol, which provides a cooling sensation, is a common constituent of after-shaves. 

A typical formulation of a good commercial item is given in Ref 3, p 362 as Sr nitrate 74, K perchlorate 6, sulfur 10, grease or wax 2—6, and sawdust or hardwood shavings 8—4%. Closely related formulations have been reported by Weingart (Ref 1)... 

Among the more interesting and reasonable results published are a series of studies demonstrating the delivery of the melanotropic peptide [Nle", D-Phe ]-ot-MSH across mouse and human skin from a relatively mild formulation consisting of 1 3 v/v PEG 400-PEG 3350. ° In vivo across shaved mouse skin, in fact, it was possible to show induction of melanogen-esis. Unfortunately, however, these data remain at best semiquantitative no actual flux values were measured precluding comparison with other work in the field. 

Aftershave gels also require an adjusted flow behaviour. They should be easily spreadable without running off the face before the shave. Microemulsions can be used to formulate clear aftershave gels with very good sensorical properties. A promising base formula is made from a combination of a cross-linking polymer with an o/w microemulsion [7]. 

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