Ingredients for cosmetics and personal care

Most cosmetic and personal care batches are water, humectants and oils plus a few functional ingredients, so a handful of bulk raw materials decide how a product looks, feels and keeps. Glycerin USP is the standard humectant in lotions, serums and soaps, and propylene glycol USP works as a humectant, solvent and carrier. Deionized water keeps calcium and magnesium out of the formula, where they can destabilize emulsions and form scum with soap. Castor oil USP gives lip products their gloss and helps disperse pigment in color cosmetics.

Soap makers use sodium hydroxide for bar soap and potassium hydroxide for liquid soap. Citric acid brings finished products down to their target pH and binds trace metals, d-limonene adds citrus scent and solvency, and isopropyl alcohol, acetone and ethyl acetate serve as solvents in sprays, nail polish and removers. Moving from bench samples to pallet-scale batches is where raw material consistency starts to matter most.

For cosmetics, grade decides which impurities have been tested for. The USP monographs for glycerin and propylene glycol include limits for diethylene glycol and ethylene glycol, the contaminants behind past poisonings when diethylene glycol was sold as glycerin. A technical-grade drum with a high assay has not been tested for them.

ACS reagent grade is a laboratory purity standard. It is very pure, but it is not a cosmetic or drug standard, and its tests differ from the monograph. For a product that is also an over-the-counter drug, such as a sunscreen, antiperspirant or anti-dandruff shampoo, ingredients generally need to meet the USP or NF monograph. Citric acid monohydrate and anhydrous citric acid both adjust pH well, but they are not interchangeable by weight.

In the United States, cosmetics fall under the Federal Food, Drug, and Cosmetic Act and FDA rules in 21 CFR Parts 700 to 740, which cover prohibited ingredients, labeling and warnings. The Modernization of Cosmetics Regulation Act of 2022 (MoCRA) added facility registration, product listing, adverse event reporting and safety substantiation, and directs FDA to set fragrance allergen labeling rules. US law does not require a particular grade for most cosmetic ingredients; the maker is responsible for safety.

Products sold in Europe follow EU Regulation 1223/2009, with prohibited substances in Annex II and restricted ones, including fragrance allergens such as limonene, in Annex III. Limonene must be named on the label above 0.001% in leave-on and 0.01% in rinse-off products. REACH governs chemical registration in the EU, and TSCA governs chemical identities in the US.

• Swapping hydrate forms by weight. Anhydrous citric acid delivers about 9% more acid per pound than monohydrate, which can push a batch past its target pH.
• Buying technical glycerin or propylene glycol for a leave-on product because the assay looks high. The glycol impurity limits are only in the USP grade.
• Treating deionized water as microbe-free. Deionization removes ions, not bacteria. Keep containers closed and rely on your preservative system.
• Leaving d-limonene open. It oxidizes in air to compounds that can sensitize skin, so store it sealed with little headspace.
• Skipping a color check on a new castor oil lot before a lipstick run, then finding a shade shift in finished product.