Do you really need to wash your hair with shampoo? At first blush, you might reply with a resounding ‘yes’ to this question. But let’s take a closer look at the evidence. Is shampoo really necessary to have a healthy scalp and clean hair? The recent history of shampoo What is shampoo? How does shampoo clean hair? What are the different categories of shampoo surfactants? Anionic detergents Cationic detergents Amphoteric detergents Non-ionic detergents Natural detergents Examples of surfactants in some popular shampoos How are shampoos formulated? Are there any health risks of shampoos? Do you really need to wash your hair with shampoo? The bottom line The recent history of shampoo Shampoo, as we know it today, is quite a recent invention considering the now daily reliance on it. According to the National Museum of American History, Drene, the first synthetic shampoo, was only introduced in the United States in the 1930s. Prior to that, hair was typically washed with bar soap. Traditional bar soap is made from animal fat and lye. When mixed with hard water, it left a difficult to rinse soap scum on the hair. This resulted in hair that felt rough and dry. It was also unmanageable. And, because traditional soap didn’t lather well, there were plenty of marketing opportunities to promote new and improved hair cleansers. By the 1960s, products like Breck, Prell, and Johnson & Johnson’s baby shampoo were found in many homes. What is shampoo? Shampoo is a hair care product that is designed to clean, remove sebum, desquamating skin cells, oils, dirt and sweat from the scalp and hair. It is also designed to beautify. It is simple to formulate a shampoo that will remove unwanted oil and dirt from the hair and scalp. However, it is more challenging to formulate one that will also leave the hair soft, smooth and manageable. To be cosmetically pleasing to the consumer, today’s shampoos are expected to do several things: clean the hair and scalp condition the hair beautify the hair give it shine make it manageable Formulating shampoo is a balancing act between removing enough of the unwanted oils and dirt so the hair appears clean while leaving the hair conditioned and aesthetically pleasing to the consumer. How does shampoo clean hair? All shampoos contain surface-active ingredients substances called surfactants. They are responsible for the cleansing action of the product. When dissolved in water, surfactants, lower the surface tension between the water and oily liquid and/or a solid particle that is to be washed away. Surfactants contain both a water-soluble head and water-insoluble (or oil-soluble) tail so they are perfectly designed to interface between water and oily sebum, dirt, and desquamating skin on the scalp. Surfactants can be ionic, nonionic or plant-based. Depending on the charges of the hydrophilic (water-loving) head, ionic surfactants can be classified as anionic (negatively charged), cationic (positively charged) or amphoteric (both negatively and positively charged). Different surfactants have different characteristics. The amount and type of surfactant will determine the product’s ability to clean and condition the hair. Each surfactant has its own potential to lather as well as cause dryness and/or irritation. What are the different categories of shampoo surfactants? Surfactants used in shampoo formulations can be categorized into five basic groups based on the polar charges on the head of the water-loving group. Each surfactant has a different ability to clean, condition, and even produce a lather or foam. Shampoos are often formulated with multiple surfactants in order to accommodate different levels of cleaning and conditioning based on hair type (i.e. normal, oily, permed, dyed or damaged hair). The first one named on the label is the primary detergent Anionic detergents Anionic detergents are named for their negatively charged water-loving polar group. They are the most popular surfactants found in shampoos today. These detergents are excellent cleansers. Multiple classes of anionic detergents are available with slightly different properties. Lauryl sulfates like sodium lauryl sulfate, ammonium lauryl sulfate or triethanolamine lauryl sulfate are excellent cleansers, foam well, and are easily rinsed from the scalp. Their ability to remove oil and skin debris is so effective that they may leave the hair feeling rough and dry necessitating the use of a conditioning agent as part of the shampoo formulation. Laureth sulfates also have excellent cleaning and foaming ability in addition to being able to condition the hair. Common ingredients in this class include, sodium laureth sulfate, ammonium laureth sulfate, triethanolamine laureth sulfate. Sarcosines are not very good cleansers but they are excellent conditioners. As such, they are frequently added to conditioning shampoos and dry hair shampoo products. They are rarely used as a primary surfactant due to their inability to remove oils sufficiently. Therefore they are commonly listed as a secondary or tertiary surfactant on a shampoo label. Examples include sodium lauryl sarcosinate and lauryl sarcosine. Sulfosuccinates, like disodium oleamine sulfosuccinate and sodium dioctyl sulfosuccinate, are very effective detergents commonly used in shampoos formulated for oily hair. Cationic detergents Cationic detergents are named for their positive charged polar group. The use of these detergents is limited by their poor ability to cleanse and foam and by the inability to be formulated with anionic detergents. Because these detergents can impart softness to damaged hair, they are often used in shampoos marketed for bleached and permanently dyed hair. Ammonioesters and long-chain amino esters are common examples. Amphoteric detergents Amphoteric detergents contain both a positively charged and a negatively charged polar group. Whether they behave as an anionic or cationic detergent depends on the pH of the solution. At a lower pH, they have the characteristics of a cationic detergent and at a higher pH, they act as anionic detergents. Due to their ability to foam and leave the hair manageable, these surfactants are commonly found in shampoos formulated for fine and damaged hair. In addition, because they don’t cause stinging in the eyes, they are used in baby shampoos. Examples include cocamidopropyl betaine and sodium lauraminoproprionate. Non-ionic detergents unlike anionic and cationic detergents, non-ionic detergents have no polar group. These mild surfactants can enhance the antistatic qualities of a formulation. Therefore, they are used as secondary surfactants in combination with the previously discussed ionic detergents. Examples include polyoxyethylene fatty alcohols, polyoxyethylene sorbitol esters, and alkanolamides. Natural detergents Natural detergents are found in plants such as soapwort, soapbark and the once-popular soapberries. They have recently made a resurgence as consumers demand plant-based alternatives. Several of these plant-based surfactants can foam and leave the hair quite manageable but their cleaning ability is minimal. The ingredients are a very effective marketing tool albeit they are not that effective. Examples of surfactants in some popular shampoos It can be helpful to take a look at examples of how shampoo manufacturers combine surfactants to get the desired end product. Let’s take a look at the surfactants in two different shampoos: Johnson & Johnson baby shampoo and Pantene Pro-V. Johnson & Johnson baby shampoo The ingredients in Johnson’s Baby Shampoo includes the following surfactants: Cocamidopropyl betaine, an amphoteric surfactant derived from coconut oil and dimethylaminopropylamine. Decyl glucoside a non-ionic, plant-derived mild surfactant. Sodium cocoyl isethionate a natural mild anionic surfactant derived from coconut oil. Lauryl glucoside a non-ionic surfactant from plant origin. PEG-80 sorbitan laurate a synthetic non-ionic surfactant and sodium methyl cocoyl taurate, an anionic surfactant derived from coconuts. Pantene Pro-V shampoo contains the following surfactants: Sodium lauryl sulfate, a synthetic anionic surfactant with strong cleaning ability Sodium laureth sulfate, a mild anionic surfactant with foaming action that is derived from palm kernel or coconut oil. Cocamidopropyl betaine an amphoteric surfactant derived from coconut oil and dimethylaminopropylamine. Sodium xylene sulfonate an anionic surfactant (also a hydrotrope – an ingredient that helps dissolve things in water). How are shampoos formulated? Shampoos are formulated with three main types of ingredients: 1. Functional ingredients These are the ingredients that make the shampoos work. Function ingredients in shampoo formulations include: Surfactants, the ingredients that are responsible for cleansing the hair and scalp Sequestering agents, ingredients that prevent soap scum from forming on the hair and scalp Preservatives which are necessary for all water-based products, including shampoo, to prevent contamination from bacteria and fungus 2. Aesthetic ingredients These are the ingredients that make the product cosmetically appealing to the consumer. Consumers are not interested in purchasing shampoo that has the consistency of water or that are clear and transparent. So, thickeners are added to give the shampoo substance as well as ingredients that opacify the shampoo to give it a more aesthetically pleasing appearance. Ingredients that can add sparkle or pearlescent quality may be added, again to gain the approval of the consumer. None of these ingredients have anything to do with the shampoo’s ability to clean the hair or scalp. However, they do work wonders on improving the desirability of the product. Foaming agents are often added to the formulation, as many consumers prefer their products to lather. Although unbeknownst to most consumers, the ability of shampoo to foam has nothing to do with the product’s ability to clean. And of course, fragrance, probably the most important characteristic of a shampoo that determines its likability. 3. Marketing ingredients These ingredients don’t necessarily have any added scientifically proven benefit. Instead, they appease the claims written on the front of the shampoo label and aid in the marketing of the shampoo. For example, the water-soluble ingredient vitamin C is often added to shampoo. It is touted to protect the hair from oxidative stress due to the damaging effects of the sun’s ultraviolet rays. Unfortunately, there is little science proving this claim. As a water-soluble compound, vitamin C will likely be washed down the drain as the shampoo is rinsed from the scalp. Are there any health risks of shampoos? What are the health risks of shampooing with synthetic shampoos? Although there is no known overall health risk, there is little science studying the effects of daily exposure to shampoo ingredients. So, the answer is unknown. What is known, however, is that too much shampooing can damage hair. Do you really need to wash your hair with shampoo? So, if you have a healthy scalp, do you really need to wash your hair with shampoo? For some individuals, the answer is a resounding NO. In fact, over the past several years, proponents of the ‘no-poo’ method espouse that there is no medical reason to wash the hair with synthetic shampoos and that doing so is solely determined by cultural norms. Shampooing has only become a daily essential in the past half-century. And, unfortunately, there is little, if any, research proving the health benefits of shampooing as part of our daily hygiene. The bottom line There is no good evidence that using shampoo has any health benefits or risks. However, modern shampoos have made it easier to get cosmetic outcomes that are pleasing (clean, silky, manageable hair). It all depends on how much you want to pay for it and you feel about the use of synthetic products in a world already full of chemicals. The selection of effective shampoos on skincare aisles that both clean and beautify is plentiful. Which shampoo you prefer and how often you shampoo is still mostly based on personal preference. One caveat regarding the instructions on many shampoo bottles, personally, I don’t follow them. I just wash and rinse. Source
