Hair gurus all over social media are dropping novel hair care routines, new products, and eccentric techniques. But not their “miracle products” can be hard to trust. It might be helpful to start our hair journey with some understanding of the basics.
Everyone knows the routine, shampoo to clean your hair and scalp, then condition to soften the hair. But do you know how they interact?
If not, might be beneficial to take a deeper look at these two products.
Essentially, hair is a system of working parts similar to a vehicle. But hair, like your car, requires cleaning, and regular maintenance. This is where using shampoo comes into play. Shampoos are typically thought of as “scalp cleansers”. However, they also protect and prevent hair shaft damage (Dias, 2015). Therefore, the ingredients in shampoo are carefully chosen to play a role in hair protection.
With an average of 10-30 ingredients, each ingredient in shampoo can be placed into four categories:
1) cleaning agents,
2) additives to promote stability and comfort of the shampoo,
3) conditioning agents to soften and add gloss, and
4) ingredients designed to treat problems like dandruff (Dias, 2015).
That’s right! Shampoos actually have ingredients that acts as conditioners, as well as agents that treat scalp diseases such as dermatitis, alopecia, and psoriasis to name a few (Shaprio and Maddin, 1996). But the ingredients that act as conditioners in shampoo are different than those of typical shampoo. Despite these additional agents, the main job of shampoo is to clean.
The cleaning agents in shampoo are known as surfactants. Basically, they are substitutes for soap and are able to break the connections between impurities, like dirt, and the hair shaft (Robbins, 2013). However, the majority of these cleansing agents are anionic or negatively charged particles, which leave hair tangled and with a static charge. Therefore, a “sulfateless shampoo”, which doesn’t contain the anionic surfactant, may be used to minimize the static electricity and tangles that come from anionic surfactants (Dias, 2015).
Shampoo may leave hair with a basic pH, an alkaline residue that is harmful to the hair and skin  , and if left behind this residue can accumulate and cause hair to tangle (Dias, 2015). But the use of a conditioner can minimize or decrease frizz, friction, and detangle hair (Robbins, 2013). Thus, the hair is said to be “conditioned” to a manageable and combable state.
A conditioner works by neutralizing the negative charge left behind from using shampoo. This is accomplished by adding positive charge to the hair fiber and lubricating the cuticle (Robbins, 2013).
The pH at which there is no net charge and hair is neutral is about 3.67. However, using any cosmetic product with a higher pH than 3.67 will cause your hair to become negatively charged and tangled (Dias, 2015). For this reason, conditioner contains cationic, or positively charged, surfactants which attract to the negative charge of hair after shampooing (D’Souza and Rathi, 2015). In addition, conditioner is also able to flatten cuticle scales over the hair shaft, and increase the reflectance of light off hair which enhances shine and color (Bolduc and Shapiro, 2001).
In summary, shampoo not only cleanses but protects and in some cases, treats medical conditions of the hair. However, the agents used in shampoo often leave hair in a negatively charged and less manageable state. Therefore, conditioner is used to return the hair to a neutral state.
So, what about leave-in conditioners, and deep conditioners? How do you know which ingredients to look for in a shampoo for a specific hair type? Well, that’s the start of another article!
Bolduc C, Shapiro J. Hair care products: Waving, straightening, conditioning, and coloring. Clin Dermatol. 2001;19:431–6.
D’Souza, P., & Rathi, S. K. (2015). Shampoo and Conditioners: What a Dermatologist Should Know? Indian Journal of Dermatology, 60(3), 248–254.
Gavazzoni Dias, M. F. R. (2015). Hair Cosmetics: An Overview. International Journal of Trichology, 7(1), 2–15.
Robbins CR. Chemical and Physical Behavior of Human Hair.4th ed. New York: Springer; 2013.
Shapiro J, Maddin S. Medicated shampoos. Clin Dermatol. 1996;14:123–8.