This is a guest post by GAry Neudahl
The long, hot summer days in the Midwest are coming to an end, and the busier days of fall are arriving, so perhaps it’s time to put away last month’s bath oil and start using a body wash.
Body Wash Formulation
Body washes typically consist of the following:
Water (aqua) to 100%
Thickening Agents 0 — 4%
Primary Surfactants 8 — 20%
Opacifiers or Pearlizing Agents 0 — 2%
Secondary Surfactants 3 — 8%
Suspension Aids 0 — 1%
Fragrance (parfum) 0.4 — 2%
Chelants 0 — 0.2%
Preservatives 0.1 — 1%
Conditioning Agents 0 — 25%
“Label-Copy” Ingredients q.s.
Body washes are compositionally very similar to shower gels and liquid soaps, and have higher surfactant loads than shampoos since hair has a much greater surface area upon which to generate foam. Primary surfactants are the ingredients that produce immediate and copious quantities of foam in body washes. The lauryl (linear C12) fatty chain length for anionic surfactants is optimal for foam generation in aqueous systems. Hence, the most commonly employed anionic surfactants are the salts of lauryl and lauryl ether sulfates, such as Ammonium Lauryl Sulfate and Sodium Laureth Sulfate. Laureth sulfates may be used to reduce the freezing point of clear body washes (so they don’t become hazy until they become quite cold) and/or to reduce the irritancy of lauryl sulfates.
Another way to reduce irritancy is to keep the longer chain length fatty alcohols derived from coconut oil and/or palm kernel oil (from which lauryl and laureth sulfates are typically made), while still stripping the shorter fatty alcohols, prior to sulfation. Doing so yields Sodium Coco-Sulfate, rather than Sodium Laureth Sulfate, at least on the package ingredient label! With ongoing vociferous, albeit unwarranted, attacks on sulfates (and on Sodium Lauryl Sulfate in particular), other surfactants, including alkyl glucosides, taurates, sulfosuccinates, and others, are finding wider application in body washes.
Secondary Surfactants and more
Foam volume, richness and stability are boosted (and, by judicious selection, body wash irritancy reduced) with secondary surfactants that typically include nonionic and amphoteric surfactants such as Cocamide MEA, Cocamidopropyl Betaine, Disodium Lauroamphodiacetate and Cocamidopropyl Hydroxysultaine. These secondary surfactants typically reduce the critical micelle concentration of the product, which means there is less free surfactant present to induce an irritation response.
Fragrance (parfum) is almost always included in body washes. It may be present as a compounded product or as a combination of essential oils, often at rather high levels. In an increasing number of markets, if known fragrance allergens are present in the product, they must be listed individually in the ingredient listing.
Preservatives are almost always needed in body washes given their high water content and the consequential potential for microbial growth. The most cost effective approach to body wash preservation is typically the use of formaldehyde donors (preservatives that work at least in part by releasing low levels of methylene glycol (formaldehyde hydrate). These include preservatives such as DMDM Hydantoin, Diazolidinyl Urea and Quaternium-15.
Special effect ingredients
To improve the feel of skin, during and after cleansing, conditioning agents including polyquaternaries (for slip) and/or superfatting agents (for softness) may be added. Using structured surfactant liquid technology, up to 25% conditioning agent, such as Petrolatum, can be added to deliver excellent emolliency to skin, while still achieving good foaming in use.
The preferred thickening agent (when composition allows it) is a simple salt, such as common table salt, Sodium Chloride. When viscosity cannot be built in this manner, polymers such PEG-150 Distearate may be used. With such polymers, the rheology of the finished product may be almost Newtonian. That means that the product would flow more like a syrup than like a styling gel.
A variety of options are available when opaque (or more opaque) appearance is desired. Fatty alcohols such as Cetyl, Cetearyl or Stearyl Alcohol may be added. Alternatively, Distearyl Phthalic Acid Amide can be used. When a pearlescent effect is desired, Glycol Stearate or Glycol Distearate are commonly utilized, although Glyceryl Distearate provides an all vegetal option.
When suspension of particulates (e.g., Titanium Dioxide- coated Mica pearlescent agents) or unemulsified droplets (e.g., Dimethicone) is required, a suspension aid such as Xanthan Gum or the earlier mentioned Distearyl Phthalic Acid Amide may be used.
Chelants such as Disodium EDTA are used to tie up multivalent ions that become part of the composition, whether through the water supply or through other ingredients. Many of these ions can promote the oxidation of unsaturated ingredients found in fragrances and elsewhere. By sequestering these metal ions (making them inactive), the chelants enhance fragrance stability and so extend product shelf life. They also enhance the efficacy of preservative systems by making it more difficult for the microorganisms to acquire these multivalent metal ions for growth.
Colorants may be added at very low level for their esthetic benefits. The use levels of these water soluble dyes are so low that skin and fabric staining are rarely if ever a concern.
And our final ingredient category is the almost always popular “label copy” ingredient. These ingredients may make up the majority of the ingredient listing, and often do so intentionally towards adding to the appeal of the product, thereby enhancing purchase intent.
And that’s it for today. If you have additional questions about body washes, or about skin cleansing products in general, you may contact the author at firstname.lastname@example.org.
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.