Shampoos represent the second biggest category in personal care and the largest in the personal cleansing and hair care segments. The principal function of a shampoo is to clean/condition hair and leave it smelling pleasant. The typical shampoo consists mainly of water, a primary surfactant, one or more co-surfactants, and a soluble salt. Other ingredients are added for thickening, fragrance, preservation, and conditioning.
The word shampoo dates back to 1762 and comes from a Hindi word meaning massage and penetrate. English hair stylists boiled shaved soap in water and added herbs to give the hair shine and fragrance. Kasey Hebert was the first known maker of shampoo, and the origin of shampoo is attributed to him. A 1914 ad for Canthrox powdered shampoo in American Magazine showed young women at camp washing their hair with Canthrox in a lake, and magazine ads in 1914 by Rexall featured Harmony Hair Beautifier and Shampoo.
Hans Schwarzkopf developed his first powder shampoo in Berlin in 1903. In 1927, he introduced the first liquid shampoo to the market and opened the Institute for Hair Hygiene, the very first training center for hairdressers.
Current shampoo usage varies significantly by region with Europeans washing their hair three times a week on average. Only one fourth of the population shampoos every day. In contrast, 80% of North Americans and 90% of Japanese wash their hair once a day.
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The main shampoo segments include:
– 2 in 1 conditioning.
– Body enhancing/volumizing.
– Color protecting.
– Shine enhancing.
– Damage repairing.
Primary surfactants are the largest single ingredient in formulations, representing ~8-15% (on an active basis) of a typical shampoo. They are typically anionic with alkyl sulfates being the primary workhorses of the shampoo industry for decades. More commonly used alkyl sulfates include sodium/ammonium lauryl sulfate, sodium laureth 3 sulfate, and sodium laureth 1 sulfate. The current trend is to use sodium laureth 1 sulfate alone as the primary surfactant. Previously the practice was to use sodium/ammonium lauryl sulfate in combination with sodium laureth 3 sulfate to improve mildness and foam quality.
The secondary, or co-surfactant, represents ~2-6% (on an active basis) of a shampoo formulation. The function of the secondary surfactant is to thicken, improve mildness, and to increase the foam stability/density. Co-surfactants function by forming a mixed micelle with the anionic surfactant, which reduces the charge repulsion of the micelle and causes the formation of elongated micelles. The larger micelle improves mildness and increases the viscosity.
Typical secondary surfactants used include cocamidopropyl betaine (most commonly used), disodium cocoamphodiacetate, and coco/lauryl betaine. Cocamide MEA is also added in many formulations as an additional cosurfactant/thickener.
Salt is another common ingredient used in shampoos from .5-2%. Salt thickens shampoos by reducing micelle charge density, helping to promote the conversion of spherical to rod shaped micelles. Sodium chloride is typically used. However, divalent salts like magnesium sulfate are more efficient if compatible with the primary surfactant in the formulation. When using salt, be aware that the formulation viscosity will decrease at reduced temperatures.
Thickening polymers are used with salt in formulations especially when suspending solids. Typically, these are anionic acrylate polymers with a low level of hydrophobic substitution and are used at ~2% active polymer with or without .5-1% salt.
Another common ingredient found in conditioning shampoos is a cationic polymer with or without silicone. The conditioning polymer helps provide wet hair conditioning, antistatic-reduced fly away, improved foam and lather, improved deposition of lipids/particles and reduced irritation. Hydroxypropyltrimonium guar and Polyquaternium 10 are the most commonly used polymers typically between .1-.5%. The most frequently used silicones are high molecular weight dimethicone and amodimethicone.
Current shampoo trends:
- Sulfate-free. Sulfate-based surfactants were reported to promote hair color fading and be more irritating. Sulfate based formulations, however, can be very mild if formulated correctly.
- Silicone-free conditioning.
- Shampoos infused with natural oils.
- Dry shampoos. The dry shampoo category has gone from 1% of all new shampoo products in 2009, to 5% in 2014, according to Mintel.
- Less shampooing due to concerns of over stripping hair and exposure to chemicals (“no poo”).
- Naiman, Ingrid. 2004. "Soap 101. History of Shampoo and Soap." Kitchendoctor.com
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