Cosmetic Chemistry 101

Source: beauty school

Chemistry is the study of composition, structure, properties and change of matter.[1]

Why is this important to us as makeup enthusiasts? It is important to know what materials we are putting on our body and how they affect us.

For example, our skin is at a pH of 5.4-5.8,[2] so we don’t want to introduce products that will neutralize our skin to a pH of 7 [the exact mid point between a base and acid], as this can increase the chance for infections from yeast/bacteria.[3]

It is important to note that chemical/synthetic does not equal bad, and natural does not equal good.

One of the reasons why I was motivated to do this is because there tends to be a huge cultural shift towards emotions and marketing vs real facts.

Don’t be afraid of science. No one that truly practices science should put you down for trying to learn. I do take problem with people that say “products that use chemicals are bad for you! I use all natural products.”

I’d like to point out chlorine is a natural occurring element. That does not make it good for you. Ammonia also occurs naturally, and if you ever used conditioner it is also in there. That doesn’t make it bad! Also, cyanide also occurs naturally. No one wants to put cyanide on their face.

NO PRODUCT IS CHEMICAL FREE. Chemical is not the same thing as toxic. It just means that there are bonded atoms used WHICH DOESN’T MEAN THEY ARE BAD.

Source: Scientific American

See this pretty good article in Scientific American.

Basic Chemistry Terms

  • Chemical: A substance that has constant composition (molecules, atoms, etc) that can not be changed unless chemical bonds are broken. [4] These can exist as solids, liquids, gas, or plasma. Chemical DOES NOT mean synthetic.
  • Atom: Smallest particle still characterizing a chemical element(e.g. gold, sodium, silver, tin, iron, etc). It has a nucleus with a positive charge, and outside “rings” of x electron(s). [5]
  • Synthetic: A “man-made” compound composed of two or more different types of atoms, made in a chemical reaction.
  • pH: The measure of the acidity or basicity of an aqueous (read water-like) solution on a scale of 0-14. Click this picture to see scale with common household items. This is very important when you consider what you are putting on your face (see first example at top), your hair, etc.

    Source: get well, stay at home

    • pH>7 = basic
      • i.e. 8 – 14
      • e.g. bleach, baking soda, ammonia, etc
    • pH=7 = neutral
      • i.e 7
      • e.g. distilled water
    • pH<7 = acidic
      • i.e. 0-6
      • e.g. lemon juice, vinegar, stomach acid
  • Solubility: The amount a substance (called a solute) will dissolve in a solvent. [6]
    • Like dissolves like, i.e a non polar substance (e.g. oil) will not dissolve a polar substance (e.g. water).
    • Cleansers: Paula’s choice had something really good on oil cleansers vs water cleansers which you can read for yourself here. I’ll go more into this, but basically her claims are that oil-cleansing is a fad based on like dissolves like. [7]
  • Hydrophilic: Something that attracts water (hydro = water, philic = like)
  • Hydrophobic: Something that repels water (hydro = water, phobic = dislike)
  • Chemical Change: A change in a material that changes it’s chemical properties (i.e. chemical bonds are broken or made)
  • Physical Change: A change in material that changes its physical properties, i.e. texture, appearance, color without changing its chemical properties.

Note, these are just some terms that may show up in the next couple of posts. This is not all encompassing and most likely will be edited.

I encourage you to check out resources such as:

Future Topics (in no particular order)

  1. Surfactants
  2. Emulsions
  3. Fatty Acids
  4. Silicones
    • with discussion on water-based vs silicone-based
  5. Polymers
  6. Sulfate-free products
  7. Ingredients


[1] Merriam-Webster dictionary

[2] Ehlers, C; Ivens, U.I.; Moller, M.L.; et al. “Females have lower skin surface pH than men.

[3] Knor, T; Meholjić-Fetahović, A; Mehmedagić, A. “Stratum Corneum Hydration and Skin Surface pH in Patients with Atopic Dermatitis”

[4] IUPAC Gold Book. “chemical substance”

[5] IUPAC Gold Book. “atom

[6] University of Wisconsin. “Solubility.”

[7] Paula’s choice. “Oil-cleansing method.”


Intro :)

Hi everyone!


This is a collection of posts I’ve made elsewhere (mainly reddit), about chemistry and beauty. 350 nm comes from the range of the visible light spectrum (~400-750nm). As of now, a lot of the posts will be made about cosmetic chemistry. I have a B.S. in Physics/Chemistry, but have since switched into engineering and have worked in Pharma. However I am a makeup enthusiast, and wanted to combine my interests.

Cosmetic Chemistry is something that really interests me, and I want to try and add facts to a lot of the marketing and opinions we see today. As always, let me know if you have questions.




reddit =, a content-aggegrate site.

nm = nanometers