Dear Valerie: What’s the best way to incorporate ceramides into a formulation without them precipitating out in stability? Do they require a specific heating phase or solubilizer?  — SARAH MIDE

Dear Sarah, 

Whether for skin or hair, I love ceramides. In hair, they play a role in protecting the keratin fiber once it loses its naturally occurring 18-Methyleicosanoic Acid layer on the outermost layers. In skin, ceramides comprise nearly 45% of the lipids found in the stratum corneum. They are produced naturally through metabolic processes, and the percent content found within in skin can change seasonally. This explains why—if you are currently located in the northern hemisphere and are reading this in January—your skin feels a little drier and itchier during these colder months. Ceramides are at their highest levels in the summer, and lowest in the winter.

If you would like to learn more about ceramides in detail, Happi magazine has produced for Evonik an e-book that is available for downloading. I wrote an article for this issue that provides historical detail about the discovery of ceramides in medical literature and their subsequent use in cosmetics. 

In that article (I’ll wait for you to go download it!) there is a beautiful chart showing the molecular structure of ceramides. When you see the structures, you might understand why ceramides—in their neat form—look and behave the way they do.

Ceramides have a super long fatty tail with few double bonds. The longer the fatty acid tail and more hydrogenation a molecule has, the higher the melting point generally is. The molecules also pack more tightly together, which explains why you need a chisel and striking tool to loosen what you need to weigh out for your batch.

Their structure also explains why many formulators and manufacturers have a difficult time processing ceramides. As you indicated, they can either precipitate out or fail to incorporate at all. Fortunately, there are a few things you can do to during processing to make your and your production team’s lives easier. 

Ensure the ceramides are being processed in an oil phase. As they are lipids, they are oil soluble! The more polar the oil or ester, the better for stability. Keep in mind that oil soluble doesn’t mean soluble at any temperature. Heat is required for dissolution.

Speaking of heat, you will need extremely high processing temperatures (high in view of most cosmetic emulsions requiring heat!). I recommend at least 85-90ºC with some time holding at that temperature to ensure your ceramides are fully dissolved and any crystal memory is erased. Even one little nucleation point will be enough for them to precipitate back out.

If your gut tells you processing ceramides in this fashion may be challenging for your manufacturing equipment, consider using a blend. Ceramide blends are often optimized with other materials like lecithin and low HLB emulsifiers to make incorporation and stability much smoother. Be mindful of the percent activity of the ceramides and adjust for the active use level you desire.

Ceramides are quite effective between 0.05 and 0.1%. You can use higher levels, but it can also lead to trouble in stability. For example, cold temperatures are not kind on any oil, wax or lipid prone to crystallization. Ceramides are also prey. If you have crystallization during freeze thaw, and you feel the ceramide was processed correctly, try lowering your use level or shore up your water phase with an adequate amount of glycols or diols, or polymer like carbomer.

You may have noticed I didn’t mention solubilizers. Due to their structure, overall hydrophobicity, and processing requirements, it is not possible to take a standard solubilizer and incorporate ceramides like you would any other lipophilic component. Solubilizers simply can’t perform the same work to incorporate or stabilize ceramides as well as a robust oil phase and appropriate emulsifiers.

Looking for more answers? In our December issue, Dear Val also answered questions about foundation color change and regulations surrounding impurities. You can find all of Valerie George’s insights here.

Valerie George

askvalerie@icloud.com

Valerie George is a cosmetic chemist, science communicator, educator, leader, and avid proponent of transparency in the beauty industry. She works on the latest research in hair color and hair care at her company, Simply Formulas, and is the co-host of The Beauty Brains podcast. You can find her on Instagram at @cosmetic_chemist or showcasing her favorite ingredients to small brands and home formulators at simply-ingredients.com