Shampoos, Harsh, Mild and Otherwise

I've examined a number of shampoos (those that I had, I did not buy any for this project) to test the notion that certain detergents (surfactants) are harsh and others are not. I did this through examination of hairs in the shampoo under a transmitted light microscope, in comparison to those hairs dry or in distilled water. When hair is well-saturated with water, it swells. But different hair swells different amounts. Hair treated with coconut oil doesn't swell as much. Fine hair doesn't swell as much. Undamaged hair without many porosities swells less than damaged hair. I measured some hairs, dry vs. wet and found quite a difference in the amount of swelling in water.

Pufferfish, all puffed up.

Pufferfish, not yet puffed up.

Never the less, water alone makes hair swell and in so doing, causes the normally-flat cuticle to lift and this creates porosities for things to leak out or diffuse in. Wetting hair alone has a "damaging" quality. Think of a pufferfish to get the right image of what happens to the cuticle when the hair swells.

Some shampoos dramatically increase this swelling. Detergents are "wetting agents" they make water - which dissolves so many things, even more "wet" and allow more things to be washed away by water. That's an oversimplification, but it's good enough for now because the pictures are the feature of this post. Detergents also can remove oils and soils. Some detergents are very good degreasing agents and some are not. The latter are the ones you want for your skin and hair. Clean is good, but too clean is irritating!

Now the fun part:
These hairs are mostly normal porosity or not porous - not chemically treated but have some damage from sun/heat from the sun, combing and brushing and daily life. I have placed them in what some people call a "sulfate shampoo" (see below).

sulfate shampoo

sulfate shampoo, arrows show raised cuticle

Yikes!

Green/yellow stripes from shampoo uptake

Shampoo with ammonium lauryl and laureth sulfate. Do you see the frilly and ragged edges? You might not want to do this too often. The picture directly to the right is a white hair which has actually held on to the color of the shampoo after rinsing (it was green). These are very effective degreasing detergents.






This is a shampoo with decyl glucoside, lauryl glucoside and cocamidopropyl betaine - Burt's Bees Super Shiny shampoo. Very little visible change taking place. The "glucosides" are regarded as mild - not strong degreasers but good "wetting agents." You can see the cuticles appear to lie smoothly and the edges do not look ragged or frilly.

Burt's Bees

Burt's Bees

Soap bar

This is hair in the "suds" or lather of a soap bar. The non-porous, very fine hair (at left) fared worse than the coarser (thicker) hair shown below. The pH of soap and shampoo bars is high because of the reaction of oils and fats with lye or another hydroxide (strong base) which is how you get oils/fats to turn into soap. This is harsh to hair. Rinsing will immediately begin to restore the hair to its own pH and the hair begins to look normal again. An acidic rinse will speed that process (though both acids and bases can damage hair), and also help remove soap scum which accumulates when oils in soap bond to minerals in hard water.

soap bar

soap bar

Dilute C12-14 olefin sulfonate 

Dilute C12-14 olefin sulfonate

To the right are hairs in a shampoo containing olefin sulfonate, which can be a strong detergent under some circumstances.  It removes oils and soil quite well. This particular shampoo, however, has conditioning agents added and a low concentration of detergent, so you don't see much happening. Concentration matters as much as the actual "harshness" or effectiveness of a detergent.

Concentrated C12-14 olefin sulfonate - see edges
of hair for raised cuticles due to swelling. This is
an ordinary concentration for shampoo.

At left is a hair in a shampoo with a higher concentration of olefin sulfonate which contained a small amount of oil, but not enough to mitigate the shampoo's harshness. Again you can see the ragged edges at left and "lifted" cuticle at right.

Concentrated "mild" shampoo

Above, right is a hair in a "gentle" baby shampoo with decyl glucoside. The detergent may be gentle, but it is concentrated shampoo with a high percent of detergent and you can see the ragged edges showing in the hair's cuticle. Below is a shampoo with the same detergent, but it has been diluted (and thickened, which causes a slightly cloudy appearance). There is little apparent change in the hair in the diluted shampoo. The dilution or reduced concentration makes a harsh detergent less harsh. Even so-called mild detergents can be harsh if they are not diluted properly in a shampoo formula.

Dilute mild shampoo

I don't mean to give the impression that shampoo is all bad! It cleans the scalp and hair more effectively than just water. Dilute shampoos with mild detergents are not very damaging to hair (visibly, anyhow) and do a good job of cleaning soils and excess oils. Even one of the harsh shampoos can be diluted at a rate of 1-2 teaspoons of shampoo in a cup of water (or halve that if it's too much volume) for a shampoo that won't cause as much stress. If you shampoo your hair daily or every other day, you might consider diluting your shampoo or choosing a mild one. The same applies to colored (dyed) hair, chemically treated hair, curly or wavy hair, or hair which gets a lot of sun or heat styling. If you want healthy, strong hair, wash it less often. Washing with a gentle or a diluted shampoo should put less stress on the hair, leading to less damage. Even an occasional wash with a full-strength detergent with good degreasing properties isn't going to "ruin" already healthy hair.