Ingredients 101: Cosmetic Ingredients Broken Down by Source, Class, and Function
Updated: Sep 6, 2019
Most of the time when I am asked a question about cosmetics by a friend or family member, the topic is ingredients. Which chemicals are safe and effective and worth searching out? Which materials could cause an adverse reaction and should be avoided?
Since there are so many cosmetic raw materials out there, it can be overwhelming. If you try to be a conscientious consumer and check out the ingredient listing on the label of products while you shop, it can feel like decoding a foreign language.
Sometimes, all it takes is a quick google search and you can find out more about the ingredient. But it can be hard to know which websites to trust. Today, I'd like to walk through some simple ways to understand an ingredient list so it is not so intimidating!
Each ingredient can be broken down into three attributes:
Source - Where the ingredient comes from. Examples: animal, plant, mineral, petroleum, bio-synthesis, fermentation
Class - Traits of the ingredient based on the chemical family. Examples: alcohols, acids, esters, polymers
Function - The role the ingredient plays in the formula. Examples: surfactants, emulsifiers, thickeners, stabilizers, preservatives
Often, the ingredient name on the label will offer clues as to one or more of the attributes above. We'll go into more detail for each and also list common ingredients and typical prefixes or suffixes that offer a clue to the source, class, or function.
Identifying the Source
When looking at the label, the name of each ingredient will often offer a clue to the source. Typical sources include: animal, plant, mineral, petroleum, bio-synthesis, and fermentation.
Note that some of the names can be from multiple sources. For example, glycerin can be animal-derived or plant-derived and therefore gly- appears in both sections. In these cases, the only way to know the true source would be additional information from the manufacturer.
Common animal-derived ingredients: beeswax, royal jelly, honey, silk, collagen, carmine, elastin, keratin, tallow
Common animal-derived names: -amide, -amine, cetyl, -glu, -gly, -lac, lan-, myrist-, -ole-, PEG, PPG, stear-, -sterol
Common plant-derived ingredients: oils and extracts with the plant name listed such as olive oil, coconut oil, rose oil, palm oil, aloe vera
Common plant-derived names: ascorb-, babassu-, cetyl-, -coc-, -glu, -gly, -lac, laur-, -lipids, myrist-, -ole-, phyto, sorb-, stear-, sterol, tocopher-
Common mineral ingredients: kaolin, bentonite, boron, clay, copper, mica, iron oxide, titanium dioxide, zinc oxide, montmorillonite, salt, pumice
Common mineral names: aluminum, cone, dime, fluoro, magnesium, phosphorous, sil, sodium, sulf, urea
Common petroleum-derived ingredients: carbomer, mineral oil, parabens, petrolatum, vinyl
Common petroleum-derived names: acetate-, -ene, -eth, isopropyl, PEG (polyethylene glycol), PPG (polypropylene glycol), PVP (polyvinylpyrrolidone)
Common ingredients: yeast, bacteria, viruses, fungi, algae, genetically modified microorganisms
Determining the Chemical Class
Many different classifications of chemicals are used as cosmetic ingredients. Most commonly used are alcohols, acids, esters, and polymers. These ingredients make up both the active ingredients and the excipients.
Alcohols are a family of chemicals that have a hydrogen and an oxygen molecule attached to a carbon. You may vaguely remember learning this in high school. It's referred to as an hydroxyl group, written as -OH. The naming convention is a suffix of -ol or -yl. Some people think of alcohols as drying agents, but that is not necessarily the case. For example, bisabolol is known to have anti-irritant, anti-inflammatory, and anti-microbial properties.
Common alcohol ingredients: isopropyl alcohol, ethanol, stearyl alcohol, cholesterol, sorbitol, panthenol, propylene glycol, butylene glycol, retinol, tocopherol, bisabolol, menthol
Acids are a family of chemicals with a pH below 7.0. Some acids are water-loving (hydrophilic) and others are fatty acids (hydrophobic). The naming convention is a suffix of -ic. Acids can be added to formulas for a variety of reasons from simply adjusting the pH to the hydrating properties of hyaluronic acid to the acne-treating properties of salicylic acid.
Common acid ingredients: citric acid, glycolic acid, stearic acid, hyaluronic acid, salicylic acid
Esters are a combination of an alcohol and an acid. The naming convention is -yl + -ate. Vitamins are often added to formulas as an ester for stability. For example, the antioxidant vitamin E is often added to formulas as tocopheryl acetate.
Common ester ingredients: isoproyl myristate, glyceryl stearate, tocopheryl acetate, retinyl palmitate, octinoxate
Polymers are large molecules formed by many repeating structural units. Some occur naturally, but most are synthetically produced. Polymer groups include gums, proteins, polysaccharides, and silicones.
Common polymer ingredients: keratin, collagen, elastin, hyaluronic acid, cornstarch, cellulose, carrageenan, guar gum, xanthan gum, carbomer, silicones, vinyl, nylon, acrylates copolymer, acrylates crosspolymer, dimethicone, cyclomethicone, cyclopentasiloxane
Understanding the Function
If you have a chemistry background, knowing the class of an ingredient will likely help you think of common attributes quickly. However, ingredients with a similar material classification may have different functions. For that reason, knowing the function of the material is also important. Common functions are surfactants, emulsifiers, thickeners, stabilizers, and preservatives.
The name surfactant comes from the phrase "surface active agent" and that is the function as well. Surfactants reduce surface tension due to their structure. Each molecule has a hydophilic (water-loving) head and a hydrophobic (oil-loving) tail. These two sections allow the molecule to function as a foaming agent or degreaser. The oil-loving tail attracts oil and dirt and the water-loving head allows it to be washed away. Surfactants can also act as foaming agents.
Common surfactants: sodium lauryl sulfate, sodium laureth sulfate, disodium lauryl sulfosuccinate, sodium C14-16 olefan sulfonate, cocoyl sarcosinate, cocobetaine
Common surfactant names: sulfate, sulfosuccinate, sulfonate, sarco, ampho, -taine
An emulsion is a stable mixture of a water phase and an oil phase. Lotions and creams are common emulsions. They require emulsifier ingredients to remain stable. Emulsifiers have the surfactant molecular structure of a hydrophilic head and hydrophobic tail. An emulsifier holds together an emulsion of water and oil by placing part of the structure in the water phase and part in the oil phase and forming a barrier between the two phases to keep the emulsion stable. Formulas often include multiple emulsifiers to thicken the formula and ensure it is stable over time.
Common emulsifiers: stearic acid, glyceryl stearate, sorbitan stearate, palmitic acid, caprylic/capric triglycerides, oleic acid, cetyl alcohol, cetearyl alcohol, stearyl alcohol, cocamides
Gums are often used to stabilize emulsions. They can be used in addition to emulsifiers in a formula to thicken the formula and increase stability. This function is supported by the polymer structure of the gum.
Common gums: carbomer, xanthan gum, magnesium aluminum silicate, acrylates copolymer, acrylates crosspolymer, guar gum, polyquaterniums
Preservatives prevent the contamination of a formula due to foreign substances such as oxidation, microbes, or products of degradation. According to the Food, Drug, and Cosmetic Act of 1938, it is illegal for cosmetic companies to sell adulterated products. Therefore, preservatives are critical components of a formula. They also ensure product stability and shelf life.
Common preservatives: DMDM hydantoin, methylparaben, ethylparaben, propylparaben, chlorphenesin, phenoxyethanol, benzyl alcohol, methylbenzyl alcohol, sorbic acid (potassium sorbate), methylisothiazolinone
Preservatives are an interesting category because they are necessary to protect the formula, but are also commonly the focus of ingredient bans. You may have seen press around bans of parabens, methylisothiazolinone (MIT), or polyaminopropyl biguanide (PHMB).
The industry is currently working on alternatives, including naturals. Essential oils may function well to slow microbial growth, but can also be common allergens. This will be an interesting field to watch.
I hope you found this summary of ingredients helpful! At the very least, I hope you now have an understanding of how to categorize different ingredients by source, class, and function. Next time you are standing in a store looking at a product's packaging, the common naming conventions should help you make sense of the ingredients and give you some insight into why each ingredient was included in the product.
Common cosmetic ingredients is a topic that could be covered in many many blog posts. I'm sure I could do a post on each subcategory with all the ingredients out there. If you have a particular category you would like to learn more about or a question related to ingredients, please let me know in the comments!