Shampoo & Conditioner - Fact Sheet

In this Article (Index)

• Shampoo
• Shampoo Ingredients
• Solid Shampoos
• Conditioners
• What are Conditioners For
• Conditioner Ingredients
• Protective Oils and Silicone

Shampoo

What is it for?

A shampoo's main purpose is to clean the hair and scalp skin, it also helps condition the hair and keep it healthy and beautiful.

The word shampoo, was adopted from the Hindi word champo linked to Sanskrit capayati = "pounds, kneads." Its original meaning was "to massage, rub the body to restore tone and vigor", first recorded in 1762. In 1860 the word extended to lathering and washing the hair.

In the 1890s, shampoos were made with shaved white Castile soap, salts (tartar, borax, potassium carbonate, or ammonium carbonate), essential oils or olive oil, and water and boiled into a creamy paste. See the recipes (i) and (ii) from that period.

Soap-based shampoos tended to be alkaline (high pH) which contributed to a dry and rough feeling on the scalp and damage to the hair cuticle.

The modern liquid shampoos date back to the 1930s, when Procter & Gamble introduced their Drene shampoo to the market as the first liquid shampoo using a synthetic surfactant which until then had been used for laundry and washing carpets.

Since then a wide range of liquid shampoos have been developed and they care for all types of hairs and scalp/hair conditions from dryness, and allergy, to dandruff, and ethnic hair varieties.

Shampoo ingredients

Shampoos as you can see by looking at their ingredients list are quite complex. For instance, P&G's Coconut Anti-Dandruff Head & Shoulders shampoo contains: Water, Pyrithione Zinc (1%), guar hydroxypropyltrimonium chloride, dimethicone, sodium laureth sulfate, sodium lauryl sulfate, TEA-dodecylbenzenesulfonate, magnesium carbonate hydroxide, zinc carbonate, trideceth-10, Zea mays (corn) silk extract, cocos nucifera (coconut) fruit extract, glycol distearate, benzyl alcohol, methylisothiazolinone, methylchloroisothiazolinone, sodium xylene sulfonate, cocamidopropyl betaine, sodium chloride, fragrance, dimethiconol, sodium benzoate, yellow 5, red 33, blue 1.

We will mention each of these ingredients as we describe their purpose below (they will be underlined).

Ingredient description

Water

The vehicle and main ingredient. Liquid shampoos are formulated using water, which makes up roughly 75%-85% of the product.

Detergents

A liquid shampoo contains synthetic detergents. These belong to four categories, and shampoos usually contain a blend of two to four of them depending on their purpose.

A shampoo for oily hair will contain detergents that remove sebum, while a shampoo for dyed or waved hair will use milder detergents that don't strip away too much sebum.

Anionic Detergents

These are the harshest, stripping most of the oil from the hair strand. They are deep cleaning. There are four groups of them: (I) Lauryl sulfates are mostly sodium lauryl sulfate, with triethanolamine (TEA) lauryl sulfate, and ammonium lauryl sulfate as secondary cleansers. (II) Laureth sulfates like Sodium laureth sulfate. (III) Sarcosines, and (IV) Sulfosuccinates.

Nonionic detergents

Mildest of all cleaners they also provide antistatic properties to shampoos. They are combined with ionic detergents as secondary cleansers. Some examples include Polyoxyethylene fatty alcohols, polyoxyethylene sorbitol esters, and alkanolamides.

Cationic detergents

They are not very good cleaning agents and do not lather well but they provide softness and manageability so they are chosen for damaged-hair shampoos. Some examples include: Long-chain amino esters, ammonia esters, and cetyltrimethylammonium chloride.

Amphoteric detergents

They are used in baby shampoo (no eye stinging) and shampoos for damaged or fine hair as they impart manageability and foam well. They include cocamidopropyl betaine and sodium lauraminopropionate.

Detergents are accompanied by other ingredients in the formulation that provide other properties to the product.

Other Ingredients

Conditioners (In shampoo formulations)

They improve gloss, are antistatic, and reduce frizz, enhancing hair manageability. Common conditioners are hydrolyzed silk and animal protein, glycerin, silicones like dimethicone, and simethicone; polyvinylpyrrolidone, and propylene glycol. Dimethiconol is a frizz-reducing silicone conditioner, and guar hydroxypropyltrimonium chloride reduces static and frizz.

Foaming agents (surfactants)

Consumers like foam as it provides the psychological feeling that the product cleans better. Cocodiethanolamide is a foaming agent that also helps spread the detergent over the scalp and hair. They are surfactants and also help blend oils in water (trideceth-10). TEA-dodecylbenzenesulfonate plays a similar role, as an emulsifier, cleanser, and foamer.

Thickeners and opacifiers

They increase the viscosity and appearance of the product (sodium chloride - common salt, sodium xylene sulfonate, PEG-150 distearate) but don't provide any hair-cleaning effects. Glycol distearate found in the Head & Shoulders shampoo above gives it a pearlescent appearance.

Chelating agents

Also known as sequestering agents (EDTA or polyphosphates) they bind to calcium and magnesium ions found in hard water and don't allow them to precipitate as "scum" on the scalp, keeping hair bright and scalp itch-free.

pH adjusters

Shampoos tend to be alkaline, which causes the hair fiber to swell. pH adjusters such as citric acid or glycolic acid make the shampoo more acidic which in turn improves cuticle surface and the appearance, frizz, and manageability of the hair.

More Additives

Shampoos use additives to keep them stable and free of germs called preservatives like sodium benzoate, methylisothiazolinone, methylchloroisothiazolinone, parabens (frowned upon due to negative obesogenic effects), tetrasodium ETDA, etc).
Magnesium carbonate hydroxide and zinc carbonate are stabilizers.
Protein-derived compounds can temporarily mend split ends (a condition known as trichoptilosis). The protein is attracted to the keratin in the hair strand and holds the cortex fragments together.

Other additives include fragrance, vitamins (panthenol); botanicals (plant oils and extracts) like Zea mays (corn) silk extract or cocos nucifera (coconut) fruit extract that provides a mild coconut aroma and oils.
As the contact time between scalp and shampoo is far too short to provide any clinical benefits, these botanicals are mostly marketing tools.
Sunscreen can be added too.
Colorants are added to give the shampoo a certain color (yellow 5, red 33, and blue 1).

This shampoo also contains an anti-dandruff, antimicrobial compound, Pyrithione Zinc (1%)

Solid Shampoos

The original solid soap-bar presentation of shampoos has made a comeback. They are convenient to pack (air travel and liquid restrictions for carry-on luggage), and friendlier with the environment as they don't require a large plastic bottle, only recyclable paper wrapping.

A 2020 study (2) reported that liquid shampoos and conditioners can cause allergic contact dermatitis on the neck, face, shoulders, and back. The culprits are the surfactants, preservatives, and fragrances. Solid shampoos lack the surfactant (sodium lauryl sulfate) which is also an allergen, but contain coconut oil for its lathering and moisturizing effect.
Some consumers report that they may cause tangling when applying the bar to the scalp, this can be avoided by lathering the hand and using it to apply it to the hair.

Conditioners

What are Conditioners for?

Their purpose is to make hair more manageable and untangled without damaging its sheen, strength, and color.

Conditioners normally contain cationic surfactants (see below) that have a positive electric charge. The hair, which has a negative charge attracts the positively charged conditioner molecules that settle on the hair's surface.
Damaged and broken hairs have a higher negative charge so they attract more conditioner. The result is a reduction in the static electricity of the hair. The neutralized charges also flatten the scales of the cuticle against the shaft which in turn improves the reflecting properties of each strand of hair, making it shinier and smoother.

This effect also mends the tips of split hairs.

Smoothness also improves combing and makes untangling and brushing easier.

Conditioner ingredients

Like shampoos, conditioners are composed of several ingredients. A typical Pantene conditioner describes its ingredients as follows: Water, Citric acid, Sodium citrate, ethylchloroisothiazolinone, Methylisothiazolinone, Benzyl alcohol, Disodium EDTA, Phenoxyehtanol, Sodium Chloride, Mica, Yellow 5, Red 33, fragrance, dimethicone, dimethiconol, glycerin, bis-aminopropyl dimethicone/amodimethiconedimethicone, pro-vitamin B5 - Panthenol, Panthenyl Ethyl Ether, Histidine, stearyl Alcohol, Cetyl Alcohol. Below we will underline each of these ingredients as we describe their function. Below we mention them and their purpose. (4)

Water

Water constitutes 80%-90% of the total product volume and serves as a vehicle for the active ingredients.

Cationic surfactants

The main component of a conditioner, these surface active agents make up 5%-15% of the product. As mentioned further up, the surfactant provides the detangling, smooth, antistatic effect that is required from a conditioner. These surfactants figure on the label as stearamidopropyl dimethylamine, surfactant, emulsifier, and also a conditioner; cetyltrimethylammonium chloride, behentrimonium or propyltrimonium, or stearamidopropyl dimethylamine.

Conditioning agents

Glutamic acid detangles and provides strength, and Behentrimonium chloride and Behentrimonium methosulfate are antistatic and detangler agents; the latter is also an emulsifier. Dicetyldimonium chloride is antistatic, and Quaternium-18 is also an antistatic for improved combing.

Emollients

These are oily compounds that mollify the harshness of other components, mostly natural oils (jojoba, olive, grape seed, glycerin), and some are synthetic silicones such as dimethicone, dimethiconol, bis-aminopropyl dimethicone/amodimethiconedimethicone). They provide a "feel" and are even superior to natural oils in terms of film formation, shine, and luster, and act as conditioners reducing frizz.

Other Ingredients

Thickeners and Emulsifiers

Used to adjust the viscosity like sodium chloride - common salt.
Fatty alcohols (stearyl alcohol, and cetyl alcohol) act like emulsifiers helping water and oil components to mix, they are "conditioning agents" too and help spread the conditioner along the hair fiber.

pH adjusters

These ingredients lower the alkaline pH of some components to make it less aggressive for the scalp and hair, using acid products or salts like citric acid, and sodium citrate.

More Additives

Stabilizers like ethylchloroisothiazolinone, methylisothiazolinone, benzyl alcohol, disodium EDTA, and phenoxyethanol act as preservatives and germicides killing microbes that might spoil the product.

Colorants tint the product (Yellow 5, Red 33) and mica enhances the appearance. Fragrance to enhance its appeal.

Vitamins pro-vitamin B5 - Panthenol and its derivative panthenyl ethyl ether. Antioxidants like histidine.

Protective Oils

Plant-based oils or silicone polymers are an important ingredient in both shampoos and conditioners because they prevent degradation by coating the outer layer of the hair, the cuticle, protecting it. (3)

Silicones

Silicone is a manmade polymer composed of silica (Si) atoms linked together forming a backbone, with hydrogen atoms or other organic compounds lining the chain. Silicone is an odorless and inert lubricating agent. It seals the hair strands giving them a glossy, smooth finish and reducing breakage when combing.

They are used in hair conditioners and shampoos.

Silicone tends to be clingy, and hard to wash off. It causes residue buildup. Dimethicone-type silicone is the oldest one, and the most resistant to wash-off. Other silicones are easier to wash off.

They improve hair feel, shine, slip, smoothness, and texture, lower friction, frizziness, and tangling. This makes them ideal for their use in shampoos, conditioners, cuticle coats, dye creams, and hair serums.

As you have seen further up, when we analyzed the formulations, aminosilicones, and siloxysilicates are also used in shampoos and conditioners. (1)

Plant-based oils

Plant-based compounds like aloe vera, shea butter, olive oil, and jojoba oil are alternatives to synthetic silicones and fatty alcohols, they nourish the hair and provide a shiny appearance and a natural, botanical appeal.