Cosmetic excipients—surfactants, rheology modifiers, humectants, emollients, and preservatives—are fundamental in topical formulation design. For B.Pharm students, mastering their functions, mechanisms and selection criteria is vital for developing safe, stable and effective products. Surfactants enable cleansing, emulsification and solubilization; rheology modifiers control viscosity, texture and spreadability; humectants attract and retain moisture; emollients restore barrier lipids and improve skin feel; preservatives prevent microbial contamination and maintain product integrity. Examples include polysorbates and SLS; carbomers and xanthan gum; glycerin and propylene glycol; cetyl alcohol and dimethicone; parabens and phenoxyethanol. Consider HLB, pH, concentration and compatibility when formulating. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which property describes the concentration at which surfactant molecules begin to form micelles?
- Hydrophilic–lipophilic balance
- Critical micelle concentration
- Solubility parameter
- Partition coefficient
Correct Answer: Critical micelle concentration
Q2. Which surfactant type is generally most compatible with cationic preservatives?
- Anionic surfactants
- Nonionic surfactants
- Cationic surfactants
- Zwitterionic surfactants
Correct Answer: Nonionic surfactants
Q3. HLB value of an emulsifier primarily guides selection for which function?
- Preservation spectrum
- Foam stabilization
- Emulsion type (O/W or W/O)
- pH buffering capacity
Correct Answer: Emulsion type (O/W or W/O)
Q4. Carbomers (carbopol) thicken aqueous systems by which mechanism?
- Ion exchange with oils
- Hydrophobic association to form networks
- Electrostatic repulsion and chain expansion after neutralization
- Crosslinking with preservatives
Correct Answer: Electrostatic repulsion and chain expansion after neutralization
Q5. Which rheological behavior improves spreadability and reduces drip in lotions?
- Dilatant (shear-thickening)
- Newtonian
- Pseudoplastic (shear-thinning)
- Plastic with high yield stress
Correct Answer: Pseudoplastic (shear-thinning)
Q6. Glycerin acts as a humectant primarily by which mechanism?
- Formation of an occlusive film preventing transepidermal water loss
- Bactericidal activity against skin flora
- Hygroscopic attraction of water molecules from the environment and epidermis
- Covalent bonding to epidermal proteins
Correct Answer: Hygroscopic attraction of water molecules from the environment and epidermis
Q7. Which emollient is a silicone widely used for silky skin feel and water repellency?
- Isopropyl myristate
- Dimethicone
- Cetyl alcohol
- Squalane
Correct Answer: Dimethicone
Q8. Parabens exert preservative action primarily by which mechanism?
- Chelation of divalent metal ions
- Membrane disruption and enzyme inhibition in microbes
- pH neutralization
- Osmotic dehydration of microorganisms
Correct Answer: Membrane disruption and enzyme inhibition in microbes
Q9. Which preservative is commonly inactivated by strong anionic surfactants due to complexation?
- Phenoxyethanol
- Parabens
- Sorbic acid
- Quaternary ammonium compounds
Correct Answer: Quaternary ammonium compounds
Q10. The term ‘occlusive’ for emollients means:
- They attract moisture from the atmosphere into the skin
- They form a film that reduces transepidermal water loss
- They chemically repair stratum corneum proteins
- They increase skin pH to enhance enzyme activity
Correct Answer: They form a film that reduces transepidermal water loss
Q11. Which rheology modifier is associative and works well in presence of surfactants?
- Carbomer (Carbopol)
- Hydroxyethylcellulose (HEC)
- Hydrophobically modified ethoxylated urethane (HEUR)
- Xanthan gum
Correct Answer: Hydrophobically modified ethoxylated urethane (HEUR)
Q12. Which factor most influences preservative efficacy in a formulation?
- Color of the product
- Water activity, pH and preservative partitioning
- Fragrance intensity
- Packaging material only
Correct Answer: Water activity, pH and preservative partitioning
Q13. Which surfactant class typically gives the highest foaming capacity?
- Nonionic surfactants
- Anionic surfactants
- Amphoteric surfactants
- Polymeric surfactants
Correct Answer: Anionic surfactants
Q14. Which humectant may increase permeability of skin and act as a penetration enhancer?
- Glycerin
- Urea
- Petrolatum
- Cetyl palmitate
Correct Answer: Urea
Q15. A preservative effective across broad pH is:
- Sorbic acid (free acid)
- Parabens (esters)
- Benzoic acid
- Phenoxyethanol
Correct Answer: Phenoxyethanol
Q16. Which excipient reduces syneresis and stabilizes emulsions by increasing continuous phase viscosity?
- Co-emulsifier like cetostearyl alcohol
- Rheology modifier such as xanthan gum
- Hydrophobic emollient like isopropyl palmitate
- Solubilizer like PEG-40 hydrogenated castor oil
Correct Answer: Rheology modifier such as xanthan gum
Q17. Which emollient is an ester known for rapid absorption and non-greasy feel?
- Mineral oil
- Isopropyl myristate
- Lanolin
- Petrolatum
Correct Answer: Isopropyl myristate
Q18. Which parameter is most critical when choosing an emulsifier for an oil-in-water cream?
- HLB value of the emulsifier matching oil phase requirement
- Melting point of the emulsifier only
- Color of the emulsifier
- Viscosity of pure emulsifier
Correct Answer: HLB value of the emulsifier matching oil phase requirement
Q19. Which preservative system relies on low pH to be effective and is often used in acidic products?
- Phenoxyethanol
- Parabens
- Benzoic acid and sorbic acid (weak acids)
- Quaternary ammonium compounds
Correct Answer: Benzoic acid and sorbic acid (weak acids)
Q20. What is the likely effect of adding high concentrations of humectants on preservation?
- Increased preservative efficacy due to higher water activity
- No effect on preservation
- Possible reduction in preservative effectiveness due to reduced free water and interactions
- Immediate sterilization of product
Correct Answer: Possible reduction in preservative effectiveness due to reduced free water and interactions
Q21. Which rheology characteristic indicates recovery of viscosity after shear is removed?
- Thixotropy
- Dilatancy
- Viscoelasticity
- Newtonian flow
Correct Answer: Thixotropy
Q22. Sorbitol and propylene glycol are examples of excipients used as:
- Emulsifiers
- Humectants and solvents
- Antioxidants
- Gelling agents
Correct Answer: Humectants and solvents
Q23. Aqueous creams stored in warm conditions showing phase separation most likely need adjustment of:
- Preservative type only
- Emulsifier concentration or type and rheology modifier
- Fragrance level
- Color additives
Correct Answer: Emulsifier concentration or type and rheology modifier
Q24. Which surfactant is gentler and often used in baby cleansers due to mildness?
- Sodium lauryl sulfate (SLS)
- Sodium laureth sulfate (SLES)
- Alkyl ether sulfate
- Betaine (zwitterionic) like cocamidopropyl betaine
Correct Answer: Betaine (zwitterionic) like cocamidopropyl betaine
Q25. Which testing assesses preservative performance in a finished cosmetic product?
- pH stability test
- Challenge (preservative efficacy) test
- Viscosity profile only
- Thermal cycling for color
Correct Answer: Challenge (preservative efficacy) test
Q26. Which emollient class is most likely to improve spreadability and act as a solvent for lipophilic actives?
- Fatty alcohols (e.g., cetyl alcohol)
- Mineral oil
- Fatty esters (e.g., isopropyl myristate)
- Polysorbates
Correct Answer: Fatty esters (e.g., isopropyl myristate)
Q27. Which combination can reduce preservative activity by complexation with metal ions?
- EDTA (chelating agent) increasing preservative activity
- High levels of chelators only
- Hard water ions reducing available preservative via chelation
- Fragrance components enhancing preservative
Correct Answer: Hard water ions reducing available preservative via chelation
Q28. When formulating anionic surfactant-based shampoo, which preservative class is typically avoided due to incompatibility?
- Phenoxyethanol
- Parabens
- Quaternary ammonium compounds (cationic)
- Sorbates
Correct Answer: Quaternary ammonium compounds (cationic)
Q29. Which rheology modifier requires neutralization (e.g., with triethanolamine) to achieve maximum thickening?
- Xanthan gum
- Carbomer
- Hydroxypropyl methylcellulose (HPMC)
- Guar gum
Correct Answer: Carbomer
Q30. Selecting a preservative for an anhydrous emulsion (low water activity) often requires what consideration?
- Use high levels of water-soluble preservatives
- No preservative needed if anhydrous
- Include preservative active in the continuous phase or use water-free antimicrobials effective at low water activity
- Rely only on packaging for protection
Correct Answer: Include preservative active in the continuous phase or use water-free antimicrobials effective at low water activity
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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