Dermatologists are routinely solicited advice by the patients regarding which shampoo to use. With the wide plethora of options available and extensive marketing of individual products, it is essential to know the basic chemistry of a shampoo. The primary ingredients of any shampoo include surfactants, conditioners, thickeners, sequestering agents, pH adjusters and preservatives. Surfactants in shampoos are used primarily for cleaning hair which involves removing sebum and dirt from the hair. Hair conditioners are added to improve hair manageability, decrease hair static electricity and add lustre. The choice of surfactant in a shampoo greatly affects how the shampoo performs as a whole. The challenge is to remove just enough sebum to allow the hair to appear clean and leave behind enough conditioning agents to leave the hair soft, shiny and manageable.1
Types of Shampoos:
Shampoos are classified based on the chemical nature of the primary surfactant/ detergent. Surfactant is an amphiphilic molecule with both lipophilic and hydrophilic ends. The lipophilic sites help bind sebum and oily dirt while hydrophilic end binds to water, allowing removal of the sebum while washing with water.
- Anionic Surfactants: Anionic surfactants carry a negative charge when ionized. It provides a lot of the lather and detergency in the shampoo. This leads to excellent cleaning, foaming, and solubility properties. However, the excessively cleaned hair is harsh, rough, dull with frizz and prone to tangling. Frequently, other surfactants and ingredients are added to reduce skin irritation.2The most commonly used anionic surfactants are sodium laurethsulphate, sodium lauryl sulphate and sulfosuccinates.
- Cationic Surfactants: Cationic surfactants carry positive charge when ionized. They are poor cleansers and do not lather well and are not compatible with anionic detergents, limiting their utility. Cationic molecules have the ability to cling to wet surfaces by static attraction. Consequently they are not easily removed during the rinsing process and form the basis of conditioning. As a result, they are useful in imparting softness and manageability to chemically damaged hair and so are primarily used as daily shampoo for damaged hair such as in case of permanently dyed or chemically bleached hair.2Polyquarternium-10 is one of the most common cationic conditioners.
- Nonionic Surfactants: Nonionic surfactant has no charge to the molecule. These are not used as a cleaning agent, but rather used in combination with the primary cleanser to modify its actions, they aid in solubility, modifying foam, and in some instances conditioning. These include cocamide DEA or coco glucosides.
- Amphoteric Surfactants: This class of surfactants contains both positive and negative charges when ionized in water.They are quite useful in decreasing the irritancy of a formulation while increasing the active contents level of the product and quality of the lather produced. Most amphoteric shampoo surfactants are used in baby shampoos, because they are gentle and will not burn the eyes. By far the most used is cocamido propyl betaine, or occasionally cocamido betaine.
- Natural detergents: The fruit pulp of Sapindus, contains saponins which are a natural surfactant and creates a lather which leaves the hair soft, shiny and manageable. After the advent of synthetic detergents, use of natural detergents has declined. Recently, botanically based hair care products have made resurgence. The cleansing of hair offered by these products is poor and their addition is only for marketing purposes.
The anionic surfactants have the greatest cleaning power with the sulfates probably being at the top. Cationic surfactants are not always used but they can provide added conditioning to the hair. Shampoos for damaged, dry or colored hair will often contain the cationic surfactants as well. The Nonionic and Amphoteric Surfactants are not particularly great for cleansing hair but they are often used in mild shampoos.
Depending on the type and relative concentrations of the surfactants along with the added conditioners, the shampoos are marketed as following:
Clarifying / Deep Cleansing Shampoo:
A clarifying shampoo is formulated to remove product build up from the hair and scalp, leaving it fresh and clean. This is for people who frequently use styling products, such as hair spray, gel, and mousse. These contain a lot of anionic detergents and often leave the hair dry.
This is for people who want to wash their hair daily. They generally contain mild detergents and typically do not incorporate the conditioners. However, an instant stand-alone conditioner is recommended which can be applied immediately after wash.
Volumizing shampoo works to add humectants, which are non-oily substances that attract and pull in moisture from the surrounding environment. These humectants help swell a person’s hair shafts to create the illusion of thicker, fuller hair. The major ingredients found in volumizing shampoo include panthenol, wheat protein, rice protein, silk protein and witch hazel.
Moisturizing Shampoo/ Conditioning Shampoo:
A moisturizing shampoo is a type of shampoo that not only cleans the hair but that also adds a moisturizing layer to the hair. Thus, moisturizing shampoos have a hair conditioning element. These generally contain only one anionic surfactant as the cleanser with added conditioners.
Baby shampoo is for babies where mild detergent is used which is non-irritating to the eyes and achieves mild cleansing, as babies produce limited sebum. They contain the amphoteric group detergents, such as the betaines which actually numb the eye tissues to prevent stinging and irritation.
This is used for people with scalp problems like seborrheic dermatitis, psoriasis, bacterial or fungal infections. In addition to regular cleansers, they contain active agents such as Tar derivatives, corticosteroids, salicylic acid, sulfur, selenium sulphide etc.
Keratin shampoo is a hair cleaning product that has keratin protein added to it. Manufacturers assert that it will make the cortex stronger. They also claim that it will coat the cuticle, adding protection to the cortex. The result is sleeker hair that is less prone to frizzing and breaking.
pH Balanced Shampoo:
This is a shampoo that tries to keep the pH of the hair at about its natural level, around 5.0 or so. When the pH of the hair gets too high, the hair becomes too alkaline, and the cuticles open, the hair becomes dry and brittle, and the shine disappears. If the pH of the hair gets too low, on the other hand, it will become hard and rough. The pH is balanced by the addition of citric, lactic or phosphoric acid. A pH-balanced shampoo will help close the hair cuticle and is recommended for color-treated or lightened hair.
- Draelos ZD. Shampoos, Conditioners, and Camouflage Techniques. DermatolClin. 2013;31:173–8.
- Draelos ZD. Essentials of hair care often neglected: Hair cleansing. Int J Trichology. 2010;2:24–9.