Tuesday, April 21, 2009

Better crafting through chemistry: Occlusion

What the heck is occlusion? This is the way we prevent transepidermal water loss (TEWL) from our skin. (From Wikipedia: TEWL is defined as the measurement of the quantity of water that passes from inside a body through the epidermal layer - skin - to the surrounding atmosphere via diffusion and evaporation processes.) We want to trap in that water and prevent it from evaporating from our skin, and protect our skin from further damage while it repairs itself from physical assaults of the day.

All the things from yesterday's post that offer emolliency - oils, butters, cationic compounds and polymers, proteins - will help trap in the moisture, and the do to the double duty of making our skin feel softer. But there are other ingredients we can use to occlude our skin. These are called barrier ingredients, because they set up a barrier between your skin and the outside world.

Cocoa, shea, mango, and other butters are great barrier ingredients, protecting your skin from TEWL and from further damage from the outside world. Each butter has its own benefits, but the key is that they stay on the skin. (For more on butters, please check out my post on this topic!)

Allantoin is another great barrier ingredient found in aloe vera and comfrey oil. You can also buy this in a white powder you can add to your products. It can help increase the water content of the stratum corneum (and this is always a good thing!) It can promote cell proliferation and wound healing. It's soothing to skin and is anti-irritant.

You can add it as aloe vera liquid, gel, or powder, or you can use comfrey oil (but do not use this on broken skin!) to get these great benefits. You can use aloe vera to your heart's content at whatever quantities you want, but I'd keep the comfrey oil below 2%. And allantoin (the powder) can be added to your lotions at up to 2% in the cooling phase. Allantoin is water soluble, so if it is not dissolved properly, it can get gritty, but this is a fantastic addition to products intended to keep out the cold, wind, and sun.

Dimethicone is another recognized barrier ingredient. It's a silicone that offers a soft, silky feel to your products. It is oil soluble, so it's not suitable for things like toners or sprays, but you can use it in small quantities in surfactant systems like shampoos. You can get water soluble dimethicone for things like toners! Use this at up to 5% (although I prefer no more than 3%) in your creations to for both the silky feeling and the occlusion properties.

Silicones act as emollients, film formers, and barrier ingredients! All around awesome!

Waxes are great occlusive ingredients, and adding beeswax and other waxes to your lotions creates a more occlusive lotion than one without. This is the way lip balms work - they trap in the moisture on your lips to moisturize.

If you're looking a really occlusive product, look no further than the humble lotion bar. Filled with occlusive oils, butters, and waxes, you can make it really awesome by adding a little dimethicone and some aloe oil (allantoin will not dissolve in the oils, so use aloe or comfrey oil instead).

Now that you know all about the three factors for great skin care products, join me on Thursday to take a closer look at honeyquat - a cationic polymer that acts as both a humectant and an emollient!


kontakt said...

What about occlusion versus - darn, what was thatfancy word. The probability that something will cause blackheads. Strong correlation or not? (When I saw the title of the post I thought that was going to be the topic. Occlusion of pores.)

Susan Barclay-Nichols said...

Hi kontakt! I've written a post on comedogenicity here. I think there may be some association between something like cocoa butter and comedogenicity, but allantoin - a great occlusive - isn't comedogenic, neither is dimethicone. So I don't think there's a connection between occlusions and comedogenicity.

Unknown said...

Hi Susan. I see these posts are a bit old so I'm hoping you can read this one and SUPER thank you in advance for any help you can provide me with. I get that this is a bit long but I'm hoping you'll have the time to read it!! I'm from México, so here some ingredients are not easy to find in quantities that are not industrial (also my not-so great-English would be because of that). I'm desperately trying to come up with a good recipe for a magnesium chloride body lotion. I need to be able to make it in somewhat large amounts (5 litres a month). This is to supply the magnesium chloride to autistic children since we believe it could make a big difference for them. The magnesium would be diluted in distilled water in pretty important quantities (known as mag oil) so that even a small amount of the lotion can provide them with a good daily supply. Because it tastes awful they would not take an oral supplementation and as for the magnesium oil alone, the kids don’t like using it due to the itchiness factor. Since our goal is primarily to supply the Mag and although we want something that's good for the kids's skin and health, it sure needs to be cost effective so an oil in water formula is what we need. So far, we have tried with 60% mag oil (basically just a salty water) and 35% oils and + such as sweet almond and coconut oils & some shea butter. To this phase we add soy lecithin, ricin oil and bees wax as emulsifiers and vitamin E as preservative and lately have added 5% of the emulsifier tetra sodium pyrophosphate. Well, I doesn't work! It separates fast and looks awful. Also I wonder if the bees wax will create occlusion and the mag oil will not be able to penetrate their skin. Please do tell me if you have some basic formulation that we can use. Will you?
Many, many thanks! I'm Marisol from a VERY hot and humid part of México

Susan Barclay-Nichols said...

Hi Marisol. Rather than trying to make something from scratch, why not do a search in this blog for a basic lotion? I have at least a hundred of them. Lecithin, ricin oil, and beeswax aren't emulsifiers, and you need to use one. Vitamin E isn't a preservative either. You are going to find some problems using that much salt, so my suggestion is to find a basic recipe and make that, then, once it is perfected, add the magnesium oil. (Do you know if magnesium can penetrate the skin?)

Marisol said...

I am so sorry I took so long to reply!! I read yours fast and went on to try to make one of your basic recipes but it took me forever to find here some of the ingredients. I had to order the Garmall Plus from the US. Well, I finally did it and so far your recipe worked for my "mag" body lotion for the kids.!! Because all of the salt it may not be as smooth as I would like but still I'm very happy with it. To answer your question about the magnesium chloride penetrating the skin, it is YES! It's actually a lot more efficient as a transdermal therapy. THANK youuu!!

Insect Art said...

Someone on Facebook just told me that you can get in trouble for using dimethicone because that turns your product into an OTC drug. We're in the USA. Do you know anything about this ?

Susan Barclay-Nichols said...

Hi Insect Art. No, this isn't true. We can use dimethicone in all kinds of products and they aren't considered drugs. If you're making claims about your products - for instance, that dimethicone will cure something - then that's a drug and it has to be tested.

I'm trying to figure out what this person could have meant by this and where they could have gotten this idea from? Hmm...

A Fajardo said...

Hi Susan, so since cocoa butter is comedogenic, I guess it's not advisable to use on the face. Also, for people who are allergic to latex, can they still use something with allantoin?

Susan Barclay-Nichols said...

Hi A! Are allantoin and latex related?

Venus Lim said...

Hi Susan,
I tried to dissolve allantoin in water and realized that it has problem with solubility. It is only sparingly soluble in water and after looking for information, there stated that water must be heated to around 50C in order to dissolve allantoin completely. Could you please share with me how could you dissolve allantoin without heating?

Thank you.

Pei Hoong

Susan Barclay-Nichols said...

Hi Pei. I don't. I only use 0.5% and I always heat it, as I've written in the post about allantoin pinned on the right hand side of the blog, and demonstrated in at least 300 formulas on the blog.

I hope this post helps - http://swiftcraftymonkey.blogspot.ca/2009/05/better-crafting-through-chemistry_07.html

Adrienne Caulfield said...

hi susan! I've been browsing your blog for years and I'm so fascinated with your style in terms of delivering complex information!

anyway, i was wondering if occlusives (dimethicone in particular) hinder the delivery of active ingredients like antioxidants?

also, what do you think of formulating a suspended delivery serum containing ascorbic acid powder, ferulic acid and resveratrol with only dimethicone as a carrier sans water?

thank you so much for helping us better understand cosmetic chemistry!