The Curly Girl Method – what’s the science? episode 170

Question 1:

Lily says – Love the podcast, I am so glad you are back. Keep up the good work!

I would love to know the chemistry of shampoo on colored hair.

• Why does washing hair strip off the color on colored hair?
• What ingredient(s) make the color safe shampoo effective ?
• Does purple/blue shampoo keep your blonde highlights blonde?
• How exactly does it work and will it work if it’s old highlights ?

1. Washing removes color from colored hair because it opens the cuticle, swells the hair and allows the color to leach out.  Explain how hair color works.
2. Color safe shampoos don’t really have an ingredient to make them less stripping, they have less detergent so they will nominally remove less color. But the reality is that they don’t work too well. If you tested products side by side, you wouldn’t see much difference in stripping of color.
3. Blue/purple color is meant to reduce brassiness
4. Essentially a small amount of the violet or blue dye is absorbed into the hair and that offsets any brassiness color.

Question 2:

Duilia asks –  Does collagen really work in topical skin products?

Collagen does a lot of things in the body but for skin, in addition to being the scaffolding, it promotes elasticity, flexibility, it protects the lower layers of skin and the body. It’s produced by the body in many forms but for skin it comes in these tiny fibers that are meshed together to form the skin structure. It’s an important protein

Now that brings us to the main question, why is collagen put in skin products and does it really work?

There are really two reasons cosmetic makers put collagen in skin products. The main reason is because collagen is an appealing ingredient to consumers which helps differentiate the product from all the other moisturizers out there and convinces people to buy it.

The logic behind using collagen in formulas goes something like this.

Skin is made of collagen
As we age, our skin produces less collagen
The lack of collagen is one of the things that leads to sagging skin and wrinkles
So adding collagen back to skin will refresh the skin and make it look young again

It’s worth pointing out too that the type of collagen used in skin products is called hydrolyzed collagen which is collagen protein broken down into a more simplified structure. It’s nothing like the collagen is found in skin.

But we don’t want to be too dismissive. So, let’s dip into our toolbox to take a more detailed look at collagen in topical treatments. Whenever we try to decide whether any anti-aging ingredient works for the skin it makes sense to ask the three “Kligman questions” that we ask. Kligman was a famous research dermatologist who did a lot of pioneering work in the field specifically related to cosmetics.

The first question is Based on the chemistry of the ingredient, is there any scientific mechanism that could explain why it would work?  Well, we’ve already talked about that and while the way it’s done in cosmetics is dubious, there is some scientific theory upon which collagen could improve the skin. If bits of the collagen protein could get down to the collagen scaffold and then get incorporated into it, that might provide a benefit.

So the second question is “Does it penetrate to the part of the skin where it needs to be in order to work?”  If hydrolyzed collagen was to work it would have to be able to penetrate into the dermis which is where the majority of skin collagen is. Unfortunately, the molecule is too big to penetrate so for the most part it does not. Instead it stays in the stratum corneum and may provide some moisturization but that’s about it.

And then the third question is “Are there peer reviewed, double blind, placebo controlled studies demonstrating the ingredient really works when applied to real people?”  None that I could find.

So, the bottom line on topical collagen is that even though it has been used in moisturizers for years as an antiaging ingredient, there is little scientific evidence that would support using it for such purposes.

No Duilia, topical collagen doesn’t really do much in skin beyond providing a little bit of moisturization.