What is in My Shampoo?

I thought it might be interesting to do a comparison of three different shampoos, and to describe what all that stuff in them is actually supposed to do.  I don't expect companies to spend the money on including an ingredient for no reason, so what is it all for?  I know this is not something a normal person would find cool, but I'm a chemistry graduate student.  It's interesting... right?

The contenders

I chose three shampoos I had at my house.  The first is a clarifying shampoo from Suave.  Clarifying shampoos are not meant to be used every day, they are for once every week or two to remove all the build up from styling products.  I use this every so often before I do a deep conditioning treatment.  Other than this shampoo, I try to stick to sulfate-free stuff.  I'll explain why when we get there.

The Frizz-Ease is a shampoo I used to use before I switched to sulfate-free.  It says it is safe for color-treated hair, but it has sulfates.  This is a smoothing shampoo and coats hair to provide a barrier against moisture, thus preventing frizz.

The Rite-Aid product is my normal shampoo.  I wash my hair a few times a week, and this is what I use.  I used to buy the more expensive name brand, but my local drugstore has their own version now and it works just as well.

So.  What is in my shampoo? Warning: Lots of pictures and lots of science ahead!

Photo from Amazon.com.  Amazon price $0.80 for 12 ounces

Suave:

Water, Sodium Laureth Sulfate, Cocamide MEA, Ammonium Chloride, Fragrance, Hydroxypropyl Methylcellulose, Tetrasodium EDTA, DMDM Hydantoin, Citric Acid, Tocopheryl Acetate, Methylchloroisothiazolinone, Methylisothiazolinone, PPG-9, Blue 1, Red 33

Photo from Amazon.com.  Amazon price  $9.98 for 2 x 10 ounces.

Frizz-Ease:

Water, Sodium Laureth Sulfate, Coco-Glucoside, Cocamidopropyl Betaine, Glycol Distearate, Cetyl Alcohol, Cocamide MEA, Hydrolyzed Silk, Fragrance, Dimethicone, Benzyl Alcohol, PPG-9, Polyquaternium-10, Sodium Chloride, Malic Acid, Disodium EDTA, Glycine, Laureth-3, Laureth-23, Bis-Methoxypropylamido Isodocosane, DMDM Hydantoin, Methylparaben, Propylparaben

Photo from Amazon.com.  Amazon price $4.59 for 8.5 ounces.

Rite Aid Brand:

Water, Sodium Cocoyl Isethionate, Sodium Lauryl Sulfoacetate, Disodium Laureth Sulfosuccinate, Sodium Lauroyl Sarcosinate, Cocamidopropyl Betaine, Glycol Distearate, Glycereth-26, Decyl Glucoside, Fragrance, PPG-5-Ceteth-20, Divinyldimethicone/Dimethicone Copolymer, Amodimethicone, Polyquaternium-7, Polyquaternium-10, Methylparaben, PEG-55 Propylene Glycol Oleate, Propylene Glycol, Carbomer, C11-15 Pareth-7, Benzophenone-3, Benzyl Salicylate, Glycerin, Trideceth-12, Laureth-9, Tocopherol, C12-13 Pareth-3, Benzyl Alcohol, Juniperus Communis Fruit Oil, Methylchloroisothiazolinone, Rosmarinus Officinalis Oil, Methylisothiazolinone, Sodium Hydroxide, Citric Acid.

Now that my spell-check has had its seizure, let's get into what these ingredients actually do (or are supposed to do).  I'll try to group them by category, with which shampoos they are in included in the description.

Water is the first ingredient of all three, and of practically any shampoo you can buy.  It acts as a solvent for the other ingredients and makes it easier for you to distribute the product through your hair.  

water droplet

Surfactants (soaps):
Sodium Laureth Sulfate [Suave & Frizz-Ease]
This is what makes shampoo get so foamy.  There are a few ways to name what this compound does; it is an emulsifying agent, an ionic surfactant, and most simply, a cleanser.  This is the soap part of shampoo and its chemical structure allows it to surround hydrophobic substances (like hair oils) so they can be washed away by water.  This is what people will shorten to a "sulfate" and a lot of people, myself included, try to avoid them in shampoos.  My main reason is that they make my hair color fade faster, as they are a bit harsher than the other, plant-derived, surfactants.

Sodium Laureth Sulfate.  The long zig-zag carbon chain at the end is what is attracted to oil (hydrophobic}.  The other end is what is attracted to water (hydrophilic), allowing it to form micelles around the oil and wash it away.

The yellow is the long carbon chain and the white is the sodium sulfate part of the molecule.  The oil would be trapped in the middle part of the micelle.

Cocamide MEA (Cocamide monoethanolamine) [Suave & Frizz-Ease]
This ingredient comes from coconuts! It acts as a non-ionic surfactant, also foams a little bit, and helps to clean hair.  It also helps to make your shampoo more viscous, or thicker and less watery.

Lauramide MEA- the precurosor to cocamide MEA

Coco-Glucoside [Frizz-Ease]
This is another coconut-derived surfactant.  It will act similarly to Cocamide MEA.

Decyl Glucoside [Rite Aid]
Another plant-derived surfactant.  It is used a lot in shampoos that call themselves gentle.

Decyl Glucoside- Still has a hydrophobic tail and a hydrophilic head.

Cocamidopropyl Betaine [Frizz Ease, Rite Aid]
Another coconut-derived surfactant with similar properties to the above two compounds.  A lot of companies are using this in place of cocamide MEA or cocamide DEA (diethanolamine instead of monoethanolamine).  This is also an anti-static agent.

Sodium Cocoyl Isethionate [Rite Aid]
Yup.  Another one.

Photo from http://meghantelpner.com/blog/rub-on-a-little-oil-coconut-oil/
This is taking over the surfactant world

Laureth-3 and -23 [Frizz-ease] and -9 [Rite Aid]

These are both surfactants and emulsifying agents.  Can you see why?

Laureth-3.  My, what a long chain you have.

Disodium Laureth Sulfosuccinate [Rite Aid]

This is a foaming agent, and it is pretty close to a sulfate.  Not quite, but it will give you enough foam to feel like you are washing your hair and getting it clean.  For some reason, we are led to believe that nothing can clean properly without foaming up.

Compare this to Sodium Laureth Sulfate above.  Notice the similarities.

Sodium Lauryl Sulfoacetate [Rite Aid]

Foaming agent.  Are you bored of these yet?  Instead of a sulfate, a sulfite, or a sulfosuccinate group attached to the long carbon chain, this has a sulfoacetate group.  This is a plant-derived ingredient, and is not totally synthetic like sodium lauryl sulfate.  I suppose that's a plus.

Sodium Lauryl Sulfoacetate

Sodium Lauroyl Sarcosinate [Rite Aid]

This is an artificial ingredient and acts as an emulsifying agent, a foaming agent, and a viscosity-increasing component. It also has anti-static properties.  

Sodium Lauroyl Sarcosinate

PPG-5-Ceteth-20, C11-15 Pareth-7, C12-13 Pareth-3, Trideceth-12 [Rite Aid]

Surfactant, emulsifying agent, blah blah. At this point they seem to have overkill on the soaps.

PEG-55 Propylene Glycol Oleate and Propylene Glycol [Rite Aid]

Surfactant, controls viscosity. Helps to dissolve and keep other components in solution.

Emollients, smoothing, conditioning and softening ingredients:
Glycol Distearate [Frizz-Ease, Rite Aid]

This is based on fatty acids and acts as an emollient (moisturizer), as well as makes the shampoo more opaque and viscous.  The main point of this though, is to soften up your hair and scalp.

Check out those long chains!  

Cetyl Alcohol [Frizz-Ease]

This acts just like Glycol Distearate does.  It is a fatty alcohol and is an emollient and opacifying agent.  Some people with eczema can be sensitive to this ingredient.

See? More another long chain.  Things with similar chemical structures behave in smilar manners.

Hydrolyzed Silk [Frizz-Ease]

This acts as a humectant (moisturizer) and as an anti-static ingredient.  They make this by combining silk proteins (which are strings of amino acids) and treating them with certain chemicals to break apart the long amino acid chains into smaller ones.  This will give your hair a silky feel and has some conditioning properties.

Silkworm Larvae

Dimethicone (PDMS or Polydimethylsiloxane) [Frizz-Ease], Divinyldimethicone, Dimethicone Copolymer, Amodimethicone [Rite Aid for the last 3]

Dimethicone and its derivatives are silicon-based polymers.  I use PDMS at work to make molds for things.  It is super-gross to work with because it is so slippery and gets everywhere.  It's like working with lube.  However, the properties that make me complain about it in the lab also make it good for making your hair shiny.  It is listed as a conditioning and lubricating agent, which will make your hair less tangled.  A lot of people avoid silicones in their body products because they aren't water-soluble and are harder to wash out.  I don't have a problem with them.  Be careful; a lot of companies will say that their silicone-based ingredients will "REPAIR SPLIT ENDS" or other things that sound awesome.  They will smooth everything down to provide a temporary fix, that is all.  

Dimethicone.  That middle part can be repeated as many times as necessary, hence the word "polymer".  What is shown is the monomer- a single sub-unit.

Polyquaternium-10 [Frizz-Ease, Rite Aid] and Polyquaternium-7 [Rite-Aid]

Polyquaternium-10 is also known as quaternized (has a quaternary- attached to 4 non-hydrogen groups- ammonium ion in the center of the structure) hydroxyethyl cellulose.  However, this does not act like the hydroxypropyl methylcellulose that is in the Suave shampoo.  It is positively charged, which will neutralize negative charges on the hair, reducing static and helping lie flat and smooth.  This also forms a film over the hair, enhancing these particular properties.  Polyquaternium-7 has the same properties, but is a copolymer of acrylamide and diallylmethylammonium chloride.  Basically that central quaternary ammonium is the important thing. 

From www.scielo.br.See the N with 4 non-H bonds on it? Quaternary Ammonium.

Glycine [Frizz-Ease]

This is an amino acid; in fact, it is the smallest amino acid.  I have a tattoo of it.  Long story.  In shampoo it is used as a conditioning and anti-static agent, but it also has buffering properties.

This is glycine.  Now just picture it on my right hip.

PPG-9 (Polypropylene Glycol 9) [Suave, Frizz-Ease]

This is a polymer that functions as a skin-conditioning agent and a mild surfactant.

Tocopheryl Acetate (Vitamin E Acetate) [Suave] and Tocopherol [Rite Aid]

This is added to shampoo for its conditioning properties, as well as its antioxidant benefits.  Antioxidents help neutralize free radicals that can come from the environment.  There is some evidence that tocopheryl acetate can penetrate the skin, thus giving cellular antioxidant benefits. 

Tocopheryl acetate is essentially vitamin E with an acetyl group at the end from a reaction with acetone

Bis-methoxypropylamido isodocosane [Frizz-Ease]

This is straight-up an emolliating agent.

Glycereth-26 [Rite Aid]

Conditions skin, acts as a humectant, and also decreases viscosity.

Glycereth-26

Glycerine [Rite Aid]

Another conditioning agent.  

Glycerol.  Notice the similarities to the polymerized version, glycereth-26, above.

Emulsion stabilizers:

Hydroxypropyl Methylcellulose (hypromellose) [Suave]

This is a semi-synthetic polymer based on cellulose (plant fiber).  It is used as another viscosity agent, and an emulsion stabilizer.  When you have oil-based and water-based ingredients in the same product, and you shake it up (like salad dressing) you suspend little bubbles of one type inside the other type of fluid.  This is an emulsion.  Emulsifying agents usually work by embedding themselves on the boundaries of these interfaces to prevent (in one example) little bubbles of oil from joining together to make a bigger oil bubble, which continues until all the oil has separated out from the water.

This is also cellulose

Carbomer [Rite Aid]

This ingredient helps increase the viscocity of the shampoo and makes it thicker and more gel-like.  It also helps stabilize emulsions.  I'm not sure WHAT carbomer they mean, but it is generally a class of water-absorbing compounds derived from polyacrylic acid.

Chelating agents:

Tetrasodium EDTA (Ethylenediaminetetraacetic acid, tetrasodium salt) [Suave]

This is something called a chelating agent.  The function of a chelating agent is to sequester (or trap) metal ions that can be present in something, making them less active.  This can work on metal ions that may be present in the shampoo, and to some degree, to metal ions present in the water that you use on your hair to foam up your shampoo.

This is EDTA binding to a metal ion (M) so it cannot react with anything.

Disodium EDTA [Frizz-Ease]

This is just about the same as tetrasodium EDTA, but with two fewer sodium ions attached to it.  It serves the same purpose as the version with 4 sodium ions.  It loses the Na+ ions in water-based (aqueous) solutions anyway, leaving the EDTA4- ion to do its chelating thing.

Buffering agents:

Ammonium Chloride (NH4Cl) [Suave]

This is an inorganic salt (not carbon-based) and is used in shampoo to help increase viscosity and stabilize the pH.  Anything that stabilizes pH is called a buffer, and trust me, you want to be sure your shampoo is buffered!  Our bodies are very sensitive to changes in pH, whether it is on the skin or in the things we eat or in our blood.  Shampoos are usually slightly acidic, to make the cuticle lie down flat.

Ammonium Chloride

Sodium Chloride [Frizz-Ease]

Yup.  Table salt.  This will make the shampoo slightly more viscous, and to some degree, will probably act as a buffering agent.  Also, if there are ingredients in the shampoo to counter-act hard water (extra calcium and magnesium ions), sodium chloride will help stabilize them.

Malic Acid [Frizz-Ease]

This is a buffering agent, to help keep the pH on the acidic side (less than 7). It can also be part of fragrances used in the product.

Citric Acid [Suave, Rite Aid]
In small quantities, such as in shampoo, citric acid can act as a pH buffer.  It is an acid, and has a very sour taste, as you would expect.  Citric acid also has slight chelation properties, such as in EDTA.  There is not enough in this shampoo to cause skin peeling, like in a face peel, but it helps maintain the correct pH of the shampoo and preserve any oils in it.

I had a student extract citric acid from lemon juice they way they did in the early 1900s.  There are much easier ways of doing it now, but it was an interesting process to watch.  Plus, lemons smell better than acid-digested cat fur (another project done at the same time).

Sodium Hydroxide (NaOH) [Rite Aid]
Another buffering agent.  This is a base, and a pretty strong one, at that.  In some cases, this can be used to denature certain protein compounds or cells that may become present in the product.

You may know NaOH as lye or caustic soda or drain cleaner.  Don't worry, there is only a teeny tiny amount in your shampoo.  Not enough to clean your drains or burn your face off.

Antibacterials, anti-fungals, preservatives:

Methylchloroisothiazolinone [Suave, Rite Aid] and Methylisothiazolinone [Suave]

These are both in the same family of compounds, which are antibacterial and anti-fungal.  They make your shampoo stay free of nasty germies and fungi which like bathroom environments.

This is their parent molecule, isothiazolinone.   It's a biocide and a lot of people have a problem with it being introduced into waste-water systems, and thus into the environment.

DMDM Hydantoin [Suave, Frizz-Ease]

This is a preservative.  It works because as it decomposes, it releases formaldehyde, which microbes do not like.  Actually, as I recently dropped a 1 liter bottle of formaldehyde and had it shatter everywhere,  I can attest to the fact that formaldehyde is really gross.  And it burns your nose and eyes and respiratory tract.  And you have to throw your contaminated shoes and socks away and wear snowboots for the rest of the day.  In July.  Formaldehyde is nasty stuff in large amounts.  I wouldn't worry too much about the small amount that DMDM Hydantoin would impart to your shampoo.  However, it can cause problems for people sensitive or allergic to formaldehyde.  

DMDM Hydantoin

Formaldehyde

Methylparaben [Frizz-Ease and Rite Aid] and Propylparaben [Frizz-Ease]

Both methylparaben and propylparaben are preservatives (and can be found in some fragrance components), specifically, they are anti-fungals.  I know there is a movement where people are avoiding parabens of all kinds, due to a study on breast cancer tissue that showed elevated levels of methylparaben.  I don't really care.  See Robyn's blog for more.  She is sciency and more articulate than I am.

Blueberries naturally make methylparaben.

Things to make it smell good and look pretty, etc:

Benzophenone-3 (Oxybenzone) [Rite Aid]

This is actually a sunscreen.  It absorbs light in the ultraviolet range.  This is a nice thing to have in a shampoo!  Your hair and scalp need sun protection, too.  I just hope it doesn't all wash away when I condition and rinse and everything.

Oxybenzone.  The more conjugated aromatic hydrocarbons (the hexagons with lines in them- benzene derivatives), the better at absorbing UV light.

Benzyl Salicylate [Rite Aid]

This is another sunscreen.  It also has some fragrance uses, especially when there are florals involved.

Benzyl salicylate.  Rings inside the benzene rings mean the same thing as the three lines indicating double bonds.  The ring just reinforces that it's conjugated (the electrons can flow around and are shared freely amongst that structure)

Fragrance [Suave, Frizz-Ease, Rite Aid]

This just makes your shampoo smell like whatever your shampoo is supposed to smell like.  These can be any combination of various esters, acetates, alcohols, ketones, terpines, etc....

This is linalool.  It adds a woodsy, herby, lavender-like scent to products.

Juniperus Communis Fruit Oil, Rosmarinus Officinalis Oil [Rite Aid]
These oils are from Juniper and Rosemary, respectively.  They are used for their strong fragrances and to mask the scents of some of the stinkier ingredients.

Benzyl Alcohol [Frizz-Ease, Rite Aid]

This can be a fragrance ingredient (it smells light and sweet), as well as a preservative and a solvent for certain other chemicals in the shampoo.

Benzyl Alcohol

Blue 1, Red 33 [Suave]

These are dyes to give the shampoo a pretty color. 

A lot of my information came from the Environmental Working Group's Cosmetics Database  which gives information about products or individual ingredients, as well as what products contain them.  Some info and many open-source images came from wikipedia, except where cited.