Product Chemistry & Cosmetic Ingredients

The pH Scale and the Acid Mantle

pH (potential of hydrogen) measures how acidic or alkaline a solution is on a scale of 0 to 14. Below 7 is acidic, 7 is neutral (pure water), and above 7 is alkaline (basic). Each whole number is a tenfold change.

The skin's surface is protected by the acid mantle — a thin film of sebum and sweat that sits at about pH 4.5–5.5 (slightly acidic). This acidity discourages bacteria and keeps the barrier intact.

• Professional facial cleansers are formulated at roughly pH 4.5–6.5 so they clean without stripping the acid mantle.
• Soap is alkaline (around pH 9–10) and can disrupt the barrier, which is why pH-balanced cleansers are preferred.
• AHA/BHA exfoliants are intentionally low-pH (often pH 3–4) to stay active.

Emulsions and Emulsifiers

Most creams and lotions are emulsions — stable mixtures of two liquids that normally don't mix, oil and water. The agent that holds them together is an emulsifier (a surfactant with a water-loving head and an oil-loving tail).

A surfactant (surface-active agent) reduces surface tension; in cleansers it lifts oil and dirt so water rinses them away. Without an emulsifier, an emulsion separates into layers.

The Moisturizer Trio: Humectant, Emollient, Occlusive

This three-way distinction is a guaranteed exam item. Each ingredient class hydrates differently.

• Humectants attract and bind water to the skin. Examples: glycerin, hyaluronic acid, sodium PCA, urea, honey. In dry air they can pull water from the deeper skin, so they pair best with an occlusive on top.
• Emollients soften and smooth by filling gaps between cells. Examples: plant oils, fatty acids, squalane, shea butter, lanolin.
• Occlusives form a seal that blocks water loss (TEWL — trans-epidermal water loss). Examples: petrolatum, mineral oil, beeswax, dimethicone.

A complete moisturizer combines all three: a humectant to draw water, an emollient to soften, and an occlusive to lock it in.

Active Ingredients to Memorize

The exam expects you to match an active ingredient to its function.

1. Antioxidants — neutralize free radicals (unstable molecules that cause oxidative stress and aging). Examples: vitamin C (ascorbic acid), vitamin E (tocopherol), green tea, resveratrol, niacinamide.
2. Peptides — short chains of amino acids. Signal peptides (e.g., palmitoyl pentapeptide-4 / Matrixyl) tell skin to produce more collagen and elastin — the anti-aging workhorse.
3. Retinoids — vitamin A derivatives (retinol) that speed cell turnover and stimulate collagen; cause photosensitivity, so SPF is mandatory.
4. AHAs/BHA — chemical exfoliants covered earlier (glycolic, lactic, salicylic).
5. Benzoyl peroxide — an antibacterial/keratolytic that kills acne-causing Cutibacterium (Propionibacterium) acnes by releasing oxygen into the pore; sold at 2.5%, 5%, and 10%.
6. Skin-lightening / tyrosinase inhibitors — kojic acid, arbutin, vitamin C, tranexamic acid, niacinamide block the enzyme tyrosinase that makes melanin, fading hyperpigmentation.
7. Sunscreen actives — physical/mineral filters (zinc oxide, titanium dioxide) reflect and scatter UV; chemical/organic filters (avobenzone, octinoxate) absorb UV and convert it to heat.

Worked Example: Reading a Label

A serum lists 'glycerin, sodium hyaluronate, tocopherol, niacinamide.' Recognize two humectants (glycerin, sodium hyaluronate) plus two actives (tocopherol is an antioxidant; niacinamide brightens). That profile suits dehydrated, dull skin — add an occlusive and daytime SPF.

Sensitizers, Allergens, and Patch Testing

Know the difference between irritation (a non-immune reaction anyone can get from a strong active) and allergic sensitization (an immune response specific to that person). Common sensitizers include fragrance, essential oils, formaldehyde-releasing preservatives, and certain dyes. Always patch test new actives on first use.

Texas Ethics: Product Claims and Recalls

TDLR ethics rules and consumer law prohibit false or misleading product claims. A Texas esthetician must not promise a product 'cures' acne, 'eliminates' wrinkles, or makes other medical claims — that is misbranding. If a product you sell is recalled, you must stop selling it immediately, remove it from shelves, and notify affected clients — continuing to sell a recalled product is both unethical and unlawful. Retail product sales are also subject to Texas sales tax, which the licensee must collect and remit.

Cosmetics vs. Drugs: The Legal Line

The law (FDA definitions that underpin TDLR ethics) separates two product categories, and the distinction drives what you may claim.

• A cosmetic is intended to cleanse, beautify, or alter appearance — moisturizers, makeup, perfumes. It may not claim to change the body's structure or function.
• A drug is intended to diagnose, treat, cure, or prevent disease, or affect the body's structure/function — e.g., acne medication, an SPF claim, dandruff treatment.
• A cosmeceutical is a marketing term (not a legal FDA category) for a cosmetic with active-looking ingredients. It is not a legal class, so you still cannot make drug claims about it.

This is why saying a cream 'cures acne' crosses into illegal drug claims — a misbranding violation an esthetician must avoid.

Preservatives and Product Safety

Water-based products grow mold and bacteria without preservatives, which is a real client-safety issue.

1. Preservatives (e.g., parabens, phenoxyethanol, benzyl alcohol) prevent microbial growth and extend shelf life.
2. The PAO symbol (Period After Opening — an open-jar icon with '12M', '6M', etc.) tells how many months a product is safe once opened.
3. Chelating agents (like EDTA) bind metal ions that would otherwise destabilize a formula.

Discard products past their PAO or that smell, separate, or change color.

Common Exam Mistakes

The top trap is confusing humectant, emollient, and occlusive — they all 'moisturize' but by different mechanisms. Another is treating 'cosmeceutical' as a legal category that allows drug claims — it is not. Finally, do not mix up physical (reflecting) and chemical (absorbing) sunscreens, or assume soap is good for the face when its alkaline pH disrupts the acid mantle.