Unit 2: Formulation of Skin, Hair & Oral Products

Semester 8

BP809T

Formulation of Skin, Hair & Oral Products

This is the practical, applied core of Cosmetic Science. You will learn the precise formulation principles and building-block ingredients for every major category of personal care products. From designing a gentle face wash to formulating a permanent hair dye, from engineering a sensitivity-relief toothpaste to creating an effective antiperspirant—this unit transforms you from a consumer into a product formulator.

Syllabus & Topics

1Skin Care Formulations – Face Wash: A cleanser designed to remove dirt, excess sebum, and makeup without stripping the skin barrier. Building Blocks: Primary surfactant (e.g., SLES for foaming/cleansing), co-surfactant (e.g., Cocamidopropyl Betaine for mildness), thickener (Carbomer or HPMC), humectant (Glycerin), preservative (Phenoxyethanol), and fragrance. pH balanced to ~5.5 (matching skin’s natural acid mantle). Types: Gel-based, Foam-based, Cream-based, Micellar water.
2Skin Care Formulations – Creams: Moisturizing Cream: An Oil-in-Water (O/W) emulsion. Lightweight, non-greasy, easily absorbed. Contains humectants (Glycerin, Hyaluronic Acid) to attract moisture and emollients (Dimethicone) to seal it in. Cold Cream (Galen’s Cerate): A Water-in-Oil (W/O) emulsion. Heavy, greasy, provides intense occlusion. Classic formula: Beeswax + Borax + Mineral Oil + Rose Water. Primary use: Cleanser and makeup remover. Provides a cooling sensation as water evaporates. Vanishing Cream: An Oil-in-Water (O/W) emulsion based on Stearic Acid neutralized with an alkali (KOH/TEA). It ‘vanishes’ into the skin, leaving a matte, non-greasy finish. Used as a daytime moisturizer and makeup base. Advantages/Disadvantages: Cold cream is excellent for dry skin but too greasy for oily skin; Vanishing cream is lightweight but provides less moisture.
3Antiperspirants & Deodorants: Antiperspirants: Contain Aluminium Chlorohydrate (ACH) or Aluminium Zirconium salts as active ingredients. Mechanism: These salts form a temporary gel plug inside the sweat duct opening, physically BLOCKING sweat secretion. They reduce sweat by 20-50%. Classified as OTC drugs. Deodorants: Do NOT block sweat. Instead, they mask body odor using fragrance and/or contain antimicrobial agents (like Triclosan) that kill the odor-causing bacteria that metabolize sweat into volatile fatty acids. Classified as cosmetics.
4Hair Care Formulations – Shampoos & Conditioners: Conditioning Shampoo: Contains anionic surfactants for cleaning PLUS cationic polymers (like Polyquaternium-10) that deposit on hair during rinsing, providing some conditioning (the ‘2-in-1’ concept). Anti-Dandruff Shampoo: Contains specific antifungal/anti-proliferative actives: Zinc Pyrithione (ZPT – cytostatic, reduces Malassezia fungus), Ketoconazole (antifungal), Selenium Sulfide (slows epidermal cell turnover), Coal Tar (reduces itching and flaking). Hair Conditioner: An O/W emulsion dominated by cationic surfactants (Cetrimonium Chloride, Behentrimonium Methosulfate) that neutralize the negative charge on damaged hair, smooth the cuticle scales, and reduce static/tangling. Silicones (Dimethicone, Cyclomethicone) coat the hair for shine. Hair Oils: Traditional Indian formulations with Coconut Oil, Almond Oil, or Amla Oil for scalp nourishment, moisture retention, and UV protection.
5Hair Dye – PPD Chemistry: Para-Phenylenediamine (PPD) Based Permanent Hair Dye: The most widely used permanent hair coloring system globally. Chemistry (Oxidative Coupling Reaction): Step 1: PPD (a primary intermediate/dye precursor) is mixed with a Coupler (like Resorcinol or m-Aminophenol) in an alkaline vehicle containing Ammonia. Step 2: Hydrogen Peroxide (H₂O₂) developer is added, which oxidizes PPD into a reactive quinone diimine. Step 3: The reactive quinone couples with the Coupler molecule inside the hair cortex to form large, insoluble colored pigment molecules (Indo dyes) permanently trapped inside the hair shaft. Ammonia’s Role: Swells the hair cuticle to allow the small precursor molecules to penetrate into the cortex. Allergenic Risk: PPD is a potent contact sensitizer—mandatory patch testing 48 hours before application.
6Oral Care Formulations: Toothpaste for Bleeding Gums: Contains anti-gingivitis agents like Stannous Fluoride, Triclosan, or herbal extracts (Neem, Clove oil) with anti-inflammatory and antibacterial properties. Toothpaste for Sensitive Teeth: Contains Potassium Nitrate (depolarizes nerve endings, blocking pain signal transmission) or Strontium Chloride (occludes open dentinal tubules, blocking pain stimulus). Teeth Whitening Toothpaste: Contains mild abrasives (Hydrated Silica, Calcium Carbonate) for mechanical stain removal and/or chemical agents (Hydrogen Peroxide, Sodium Tripolyphosphate) for bleaching/dissolving stains. Mouthwash: Liquid oral rinse containing antiseptics (Cetylpyridinium Chloride, Chlorhexidine), fluoride for cavity protection, and flavoring agents. Chlorhexidine is the gold standard anti-plaque agent but causes tooth staining with prolonged use.

Learning Objectives

Formulate Creams: Differentiate Cold Cream (W/O), Vanishing Cream (O/W), and Moisturizing Cream (O/W) based on emulsion type, key ingredients, and clinical application.

Explain Antiperspirant Mechanism: Describe precisely how Aluminium Chlorohydrate physically reduces sweating at the eccrine gland duct level.

Design Anti-Dandruff Shampoo: List the four major anti-dandruff actives (ZPT, Ketoconazole, Selenium Sulfide, Coal Tar) and explain their distinct mechanisms of action against Malassezia fungus.

Trace PPD Dye Chemistry: Detail the complete oxidative coupling reaction mechanism by which PPD and a Coupler produce permanent color inside the hair cortex.

Select Sensitivity Agents: Explain the two distinct mechanisms by which Potassium Nitrate and Strontium Chloride each relieve dentinal hypersensitivity.

Exam Prep Questions

Q1. What is the fundamental difference between a Cold Cream and a Vanishing Cream?

The key difference lies in the type of emulsion. A cold cream is a water-in-oil (W/O) emulsion, where oil is the continuous phase, making it heavy, greasy, and occlusive; it provides a cooling sensation due to evaporation of water and is mainly used for cleansing and makeup removal. In contrast, a vanishing cream is an oil-in-water (O/W) emulsion, where water is the continuous phase, making it lightweight, non-greasy, and quickly absorbed into the skin, so it is commonly used as a moisturizer or makeup base.

Q2. Why is PPD (Para-Phenylenediamine) used in hair dye if it causes allergies?

PPD is widely used because of its unique ability to produce permanent hair color. When oxidized by hydrogen peroxide, it forms small molecules that penetrate deep into the hair cortex and then polymerize into large, insoluble colored compounds that remain trapped inside the hair shaft. This results in long-lasting, intense color that resists washing. Although it can cause allergic reactions in some individuals, alternatives generally provide less vibrant and less durable results.

Q3. How does Potassium Nitrate relieve tooth sensitivity?

Tooth sensitivity occurs when stimuli cause fluid movement within dentinal tubules, activating nerve endings and producing pain. Potassium nitrate releases potassium ions (K⁺), which accumulate around these nerve endings and depolarize the nerve membrane, reducing its ability to transmit pain signals. With regular use over time, this leads to a significant decrease in tooth sensitivity.