Face wash formulation principles MCQs With Answer

Face wash formulation principles MCQs With Answer

Understanding face wash formulation is essential for B.Pharm students preparing for careers in pharmaceutical and cosmetic sciences. This concise introduction covers core principles: selection of surfactants (anionic, nonionic, amphoteric), target pH for skin compatibility, rheology modifiers and thickeners (carbomers, xanthan), preservatives and preservative efficacy testing, solubilizers, humectants, emollients, and stability evaluation. Key concepts also include HLB balance, foam and cleansing mechanisms, irritation potential, microbial control, and regulatory quality tests. These keywords—face wash formulation, surfactants, pH, preservatives, rheology, stability testing, HLB, and syndet—will guide your revision. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which class of surfactant is most commonly used in mild facial cleansers (syndets) for reduced irritation?

• Anionic surfactants like sodium lauryl sulfate
• Cationic surfactants like benzalkonium chloride
• Amphoteric surfactants like cocamidopropyl betaine
• Nonionic surfactants like polysorbates

Correct Answer: Amphoteric surfactants like cocamidopropyl betaine

Q2. What is the primary mechanism by which surfactants remove sebum and dirt from skin?

• pH neutralization of oily residues
• Emulsification and micelle formation around oily particles
• Enzymatic degradation of lipids
• Physical abrasion of the stratum corneum

Correct Answer: Emulsification and micelle formation around oily particles

Q3. Which pH range is generally optimal for face wash formulations to match skin surface and minimize irritation?

• 2.0–3.5
• 4.5–6.0
• 7.5–9.0
• 10.0–11.5

Correct Answer: 4.5–6.0

Q4. HLB (Hydrophilic–Lipophilic Balance) is most useful for selecting which excipient in a face wash?

• Preservatives
• Thickeners
• Emulsifiers/solubilizers
• Fragrance oils

Correct Answer: Emulsifiers/solubilizers

Q5. Which polymer is commonly used to provide viscosity and gel structure in clear facial gels?

• Carbomer (Carbopol)
• Polyethylene glycol 4000
• Sorbitan tristearate
• Calcium carbonate

Correct Answer: Carbomer (Carbopol)

Q6. A preservative challenge test is performed to assess:

• Foam height and stability
• Microbial reduction over time after inoculation
• Viscosity changes under shear
• pH drift during accelerated stability

Correct Answer: Microbial reduction over time after inoculation

Q7. Which ingredient is primarily used as a chelating agent in face wash formulations to improve preservative efficacy?

• Ethanol
• EDTA (disodium EDTA)
• Sodium chloride
• Glycerin

Correct Answer: EDTA (disodium EDTA)

Q8. Which of the following is a humectant commonly included in face washes to retain moisture?

• Isopropyl myristate
• Glycerin
• Sodium lauryl sulfate
• Citric acid

Correct Answer: Glycerin

Q9. Which test helps evaluate the potential of a face wash to cause skin irritation or sensitization?

• pH measurement
• In vitro foam test
• Patch test on human volunteers
• Viscosity profiling

Correct Answer: Patch test on human volunteers

Q10. Syndet bars differ from soap primarily because they are formulated from:

• Alkaline saponified fats
• Synthetic surfactants with neutral to slightly acidic pH
• High concentrations of sodium hydroxide
• Pure glycerin bases only

Correct Answer: Synthetic surfactants with neutral to slightly acidic pH

Q11. Which preservative system is commonly avoided in anionic surfactant-rich face washes due to incompatibility?

• Parabens
• Quaternary ammonium compounds (cationic preservatives)
• Phenoxyethanol
• Sorbic acid

Correct Answer: Quaternary ammonium compounds (cationic preservatives)

Q12. Foam height in a face wash is mainly influenced by which property of surfactants?

• Melting point
• Hydrophilic-lipophilic balance and adsorption at the air–water interface
• Color and odor
• Preservative content

Correct Answer: Hydrophilic-lipophilic balance and adsorption at the air–water interface

Q13. To solubilize small amounts of fragrance oil in an aqueous face wash, formulators commonly use:

• High concentrations of salt
• Cosolvents or solubilizers like polysorbate 20
• Calcium carbonate
• Strong acids

Correct Answer: Cosolvents or solubilizers like polysorbate 20

Q14. Which rheological behavior is desirable in a face wash to allow easy dispensing but good cling during application?

• Newtonian viscosity
• Shear-thinning (pseudoplastic) behavior
• Dilatant (shear-thickening) behavior
• Thixotropic with very slow recovery

Correct Answer: Shear-thinning (pseudoplastic) behavior

Q15. Which analytical test assesses the stability of a face wash under elevated temperature and humidity to predict shelf-life?

• Accelerated stability testing
• Foam collapse test
• Patch test
• pH titration only

Correct Answer: Accelerated stability testing

Q16. Which of the following is an indicator of inadequate preservation in a face wash shown during preservative efficacy test?

• Rapid decline of inoculated microbes within 24 hours
• Growth or stable counts of bacteria, yeast, or mold over time
• Immediate color change on addition of indicator dye
• Increase in viscosity upon microbial inoculation

Correct Answer: Growth or stable counts of bacteria, yeast, or mold over time

Q17. Which ingredient can be used as a mild emollient to reduce skin tightness after cleansing?

• Sodium lauryl sulfate
• Propylene glycol
• Isopropyl palmitate
• Citric acid

Correct Answer: Isopropyl palmitate

Q18. Why is control of ionic strength important when formulating with anionic surfactants?

• Ionic strength only affects color
• It influences micelle size, viscosity, and foam stability
• Ionic strength determines fragrance volatility
• It is irrelevant for cleansing performance

Correct Answer: It influences micelle size, viscosity, and foam stability

Q19. Which test measures bacterial endotoxin contamination risk in rinse-off cosmetic products?

• PCR for viral RNA
• Limulus Amebocyte Lysate (LAL) test
• pH meter reading
• High-performance liquid chromatography (HPLC)

Correct Answer: Limulus Amebocyte Lysate (LAL) test

Q20. In foam-rich face washes, adding a small amount of fatty alcohol (e.g., cetyl alcohol) often:

• Drastically increases microbial growth
• Acts as a foam destabilizer and reduces cleanser efficacy
• Improves foam stability and sensory feel (creaminess)
• Neutralizes preservatives making them inactive

Correct Answer: Improves foam stability and sensory feel (creaminess)

Q21. Which of the following is a common method to determine the irritation potential of a face wash in vitro?

• Fragrance retention assay
• Reconstructed human epidermis (RHE) irritation test
• Pipette viscosity measurement
• Shelf-life prediction model

Correct Answer: Reconstructed human epidermis (RHE) irritation test

Q22. Which active would be included in an anti-acne face wash to reduce Propionibacterium (Cutibacterium) acnes?

• Benzoyl peroxide
• Sodium chloride
• Glycerin
• Fragrance oil

Correct Answer: Benzoyl peroxide

Q23. Which parameter is most relevant when choosing packaging for an oxygen-sensitive antioxidant in a face wash?

• Transparency of the container only
• Barrier properties against oxygen and light
• Size of the cap threads
• Color of the product label

Correct Answer: Barrier properties against oxygen and light

Q24. What role do amphoteric surfactants play when mixed with anionic surfactants?

• They inactivate anionic surfactants
• They reduce irritation and stabilize foam performance
• They make the formulation highly alkaline
• They precipitate thickeners immediately

Correct Answer: They reduce irritation and stabilize foam performance

Q25. Which parameter is commonly monitored to detect microbial contamination during stability studies?

• pH, viscosity, and total viable count (microbial load)
• Only the color of the product
• Packaging label adhesion
• Fragrance concentration alone

Correct Answer: pH, viscosity, and total viable count (microbial load)

Q26. In a face wash containing cationic conditioning agents, which surfactant class should be minimized to avoid incompatibility?

• Anionic surfactants
• Nonionic surfactants
• Amphoteric surfactants
• None—cationics are compatible with all classes

Correct Answer: Anionic surfactants

Q27. Which antioxidant is often used in formulations to protect unsaturated emollients from rancidity?

• Ascorbic acid (Vitamin C) in free form without protection
• Tocopherol (Vitamin E)
• Sodium lauryl sulfate
• Citric acid as a primary emollient

Correct Answer: Tocopherol (Vitamin E)

Q28. When formulating a sulfate-free face wash, which surfactant is a typical replacement to maintain cleansing?

• Sodium lauryl sulfate (SLS)
• Sodium laureth sulfate (SLES)
• Cocamidopropyl betaine or other mild non-sulfate surfactants
• Calcium hydroxide

Correct Answer: Cocamidopropyl betaine or other mild non-sulfate surfactants

Q29. The term “rinse-off” cosmetic implies which requirement for antimicrobial preservatives?

• No preservative is needed because product is rinsed
• Lower preservative efficacy is acceptable compared to leave-on products, but preservation is still required and tested
• Only natural preservatives are allowed
• Preservative efficacy does not need validation

Correct Answer: Lower preservative efficacy is acceptable compared to leave-on products, but preservation is still required and tested

Q30. Which formulation strategy can reduce surfactant-induced dryness while maintaining cleansing efficacy?

• Increase anionic surfactant concentration to maximum
• Include mild amphoteric/nonionic surfactants, add humectants and a small emollient
• Eliminate preservatives entirely
• Raise pH to strongly alkaline to enhance cleaning

Correct Answer: Include mild amphoteric/nonionic surfactants, add humectants and a small emollient

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