Basic Cosmetic Formulations - Bath Oils
This is a guest post by cosmetic science expert Gary Neudahl.
We’ve had a warm winter, a hot spring and a really hot and dry summer in the midwest. Perhaps you’ve thought of getting rid of the sweat and getting away from it all, luxuriating in peace and quiet, taking a nice, long bath. Maybe you’ve already been there, done that. More than once. If you’ve used a bath oil, following is what was likely in it, and why.
Bath oil formulation
A classical bath oil composition consists of:
Emollients: 85 — 100%
Antimicrobial Agents: 0 — 0.5%
Dispersing Agents: 0 — 10%
“Label-Copy” Ingredients: 0 — 0.5%
Fragrance (Parfum): 0 — 4%
Antioxidants: 0 — 0.05%
Water-insoluble emollients constitute the vast majority of the formulation. In the absence of a dispersing agent, these ingredients float on the surface of the water and, upon exiting the bathtub, leave an emollient film on the skin that enhances moisture retention and softness. Most widely utilized is petrochemically-derived Mineral Oil (Paraffinum Liquidum). Also widely used, but botanically-derived, are Prunus Amygdalus Dulcis (Sweet Almond) Oil, Helianthus Annuus (Sunflower) Seed Oil, Glycine Soja (Soybean) Oil and Simmondsia Chinensis (Jojoba) Seed Oil. Among the more commonly incorporated synthetic esters are Caprylic/Capric Triglyceride and Isopropyl Myristate. Interestingly, Dicapryl (actually, Diisoctyl, as in Di-2-octyl, from castor oil) Adipate of Avon SKIN SO SOFT fame is not widely used in bath oils.
Dispersing agents are surfactants of moderately low HLB, soluble in the emollients, that are added to cause the bath oil to “bloom;” that is, to spontaneously form a whitish milk, when dispensed into bath water or applied to moist skin in the shower. Among the more commonly utilized dispersants are Laureth-4, Laureth-3, Laureth-2, C12-13 Pareth-3 (100% petrochemically-derived) and Glyceryl Oleate (100% botanically-derived).
Bath oil fragrance
Fragrance (parfum) is almost always added (either as a compounded product or as a combination of essential oils), and often at rather high levels. As a result, contact allergens in fragrances are commonly present at levels that require separate listing on the ingredient label in some geopolitical zones. Among the most commonly listed fragrance allergens in a recent Mintel GNPD search of bath oils were Linalool, [d-]Limonene, Citronellol and Geraniol.
Antimicrobial agents are not required when the potential for contamination with water is excluded. If dilution with water (e.g., towards getting the last drop out) may occur, oil-soluble preservatives such as the parabens and, depending on the polarity of the oil phase, phenoxyethanol and/or benzyl alcohol, may be added to supply a modicum of protection against microbial growth.
Bath oils are not exempt from the propensity to include “label copy” ingredients — components added, often at vanishingly small levels, not because they are functional, but because they help catch the consumer’s interest and garner initial product trial. A diverse array of botanical extracts and oils have been utilized in the quest for enhanced purchase intent.
Antioxidants take on special importance when using ingredients with unsaturation, and especially polyunsaturation, such as triglyceride oils rich in omega-3, omega-6 and omega-9 fatty acid moieties, as part of the bath oil composition. The most commonly used antioxidant in bath oils (same Mintel search mentioned earlier) is Tocopherol, with Tocopheryl Acetate, BHT and Ascorbyl Palmitate rounding out the top four.
And that’s it for today. If you have additional questions about bath oils, or about bath products in general, you may contact the author at email@example.com.
Gary Neudahl is currently Product Application Manager, Personal Care Ingredients, for the HallStar Company and is based at the HallStar Manufacturing and Technical Center in Bedford Park IL USA.