History and Science of Soaps and Cleansers

Skin Cleansing

• October 15 is Global Handwashing Day
• Handwashing with soap and water is recommended.

History of Skin Cleansing

• Salt was used for cleansing by Chinese, Egyptians, and Greeks.
• Soap manufacturing began in ancient Babylon around 2800 BC. Methods involved boiling fats with ashes and water.
• Greeks used strigils to scrape off oil and dirt.
• Clay and sand were also used.
• Romans lived in water-rich areas. They built aqueducts to bring clean water, which made bathing popular.
• An ancient Roman legend traces soap origins to Mount Sapo (Rome), where sacrificed animal fats and wood ash mixed in the Tiber river created a cleansing clay mixture.
• Bathing declined and sanitation worsened after the fall of Rome. This led to hygiene-related diseases like the Black Death (14th century).
• Deaths of 75 to 200 million people in Europe occurred during the 1347-1351 Plague.
• Personal cleaning became popular again in the 17th century.

Ancient Soap Making

• Medieval soaps in Northern Europe were made with wood ashes and animal/fish oils.
• Resultant soaps were unpleasant smelling soft soaps.
• Soap was used in textile/clothing cleaning.
• Use for personal washing was not common in early times.
• Syria was known for its pleasant hard soaps.

Hand Sanitizers

• Hand sanitizers are adjuncts, not replacements for soap and water, according to the CDC.
• Concerns about the use of hand sanitizer as part of infection control first arose in the mid-1800s.
• The Hungarian obstetrician Ignaz Semmelweis, a pioneer in antiseptic hygiene in mid-1800s, advocated for hand washing in a chlorine solution before examining women to reduce the spread of disease. This action effectively reduced infections.

Skin Cleansers

• Skin cleansers remove dirt, makeup, environmental pollutants, germs, and other soilings from the skin.
• Examples of cleansers include facial cleansers, bath and shower products, hand cleansing products, including hand sanitizers.

Dirt Removal

• Skin is soiled with solid particles stuck to the sebum (oil).
• These substances include skin scales, dust, soot, salt, urea, bacteria, and cosmetics/makeup residue.
• Other substances carried in the air are also deposited on the skin.

Grease Removal from Skin

• Removing grease from skin involves three methods:
• Emulsification using surfactants (e.g., shower gels, shampoos).
• Dissolving excess oils with more oils (e.g., creams, body oils).
• Absorbing the oils using absorbent materials (e.g., cleansing masks, kaolin).

Soap as a Cleanser

• Soaps are made from reacting animal and vegetable fats/oils with alkalis.
• Hard soaps are sodium salts of fatty acids from animal/vegetable sources (e.g., sodium stearate).
• Soft soaps (liquid soaps) are potassium salts of fatty acids.
• Soap names came from Roman Legend.

Synthesis of Soap

• A chemical reaction between glycerol tristearate (fat) and sodium hydroxide (alkali) produces sodium stearate (soap) and glycerol.

How Soap Works

• Soap particles coat fat droplets that hold dirt.
• The soap particles and the dirt are washed away with water.

Disadvantages of Regular Soap

• In hard water, regular soap forms an insoluble scum (calcium and magnesium salts).
• This scum may stick to the skin, causing irritation.
• Regular soaps are typically salts of weak acids and strong alkalis, which results in a high pH (9-10). This may irritate skin (normal skin pH, 4-6.5).

Surfactants as Cleansers

• Water is not effective for cleaning greasy surfaces as it's repelled by oil.
• Surfactants are molecules with both water-loving (hydrophilic) and oil-loving (hydrophobic) parts.
• Surfactants are used in many cosmetic and toiletry products (e.g., detergents, foaming, conditioning, solubilization, emulsification).
• Selecting surfactant for use must consider the functions they need to fulfill in a cosmetic product (e.g., detergency, emulsification, foam quality).

Synthetic Soaps (Soapless Soap)

• Synthetic soaps are made from surfactants.
• Four types of surfactants: anionic, cationic, non-ionic, amphoteric.
• Sodium salts of fatty acids are anionic.

Detergent

• A detergent is an agent that removes dirt.
• Several types of detergents exist (mild, strong, ionic, non-ionic), depending on the type of dirt and surface.
• Three essential properties of detergents:
  • Wet the surface
  • Displace dirt from the surface
  • Solubilize the dirt in solution.

Cleansing Action of a Detergent

• Wetting: The detergent reduces the surface tension of water, allowing it to spread across a greasy surface.
• Emulsification: The detergent molecules bind to the grease, forming droplets dispersed in the water.
• Rinsing: Water removes the emulsified grease and loosened dirt.

Surfactant Classes

• Anionic (sulfates, phosphates, carboxylates)
• Cationic (quaternary ammonium salts)
• Zwitterionic/Amphoteric (amino propionates, glycinates)
• Nonionic (ethoxylates)

Anionic Surfactants

• Sodium lauryl sulfate (SLS)
  • A detergent
• Sodium C12-15 pareth-15-sulfonate
• A detergent

Cationic Surfactants

• Hexadecyl(cetyl) trimethyl ammonium bromide

Amphoteric Surfactant

• Cocoamphoglycinate

Betaines

• Coco-betaine and N-coco-N-dimethyl glycine are examples.
• Used in baby shampoos and other products to improve lather and viscosity.

Nonionic Surfactants

• Sorbitan esters (Tweens, Spans).
• No incompatibility problems with other ingredients.

Functions of Surfactants

• Detergency, foaming, conditioning, solubilization, emulsification.

Advantages of Synthetic Soaps

• Usually cause less skin irritation than traditional soap.
• The pH can be adjusted to normal skin using citric acid or lactic acid.

Lather and Foam

• Lather plays little or no role in the cleansing action of soap/detergents.
• It is helpful in some applications such as automatic washing machines, but special products("low lather") are available.
• Lather is an indicator of cleanser activity, and it holds the cleanser on the surface for rinsing.

Ingredients in Soaps and Cleansers

• Moisturizers: help counteract dryness caused by soap. Examples include glycerin, lanolin, and vegetable fats.
• Preservatives
• Coloring agents
• Fragrances
• Antibacterial substances
• pH altering substances (e.g., citric acid)
• Other ingredients

Transparent Soap

• Contains high glycerin concentrations for transparency and mildness.

Antibacterial Substances

• Antibacterial soaps often contain substances like triclosan.
• Some remain after washing and inhibit bacteria growth.
• Used to prevent body odor, acne, or hair follicle infections and following exposure to dirt or contamination.

Other Ingredients

• Other natural ingredients/Additives (Vitamins, Herbs etc) may exist but have no documented medical value.
• Soaps are in contact with the skin briefly so these additives are quickly washed off.

Mild/Hypoallergenic Soap

• Often used for people with sensitive skin and infants.
• Typically have no fragrances, coloring agents.
• Often contain surfactants from the betaine group that are known for their mildness and lack of stinging.

Soaps vs. Soapless Cleansers

• Different behavior in hard water: Soap forms scum; Soapless detergents do not.
• pH of soapless cleansers can be adjusted to normal skin, lowering irritation.

Lotions and Liquid Preparations for Facial Cleansing

• Oil-in-water emulsions: oils dispersed in water.
  • Easier to remove from the skin.
• Fresh-up pads/tissues: Tissues saturated with cleansing lotion to remove makeup.

Advantages of Creams/Liquids for Facial Cleansing

• Easy makeup removal
• Suitable for dry skin (oil content).
• Can be used further away from bathroom.

Cleansing Creams

• Designed for makeup removal, not moisturizers.
• Should be rinsed off immediately to avoid surfactant-based irritation.
• Better washed with water than wiped to remove.

Abrasive Cleansers (Scrubs)

• Creams/emulsions with tiny granules for physical skin cleaning.
• Gentle use is recommended for normal skin. Frequent use can damage sensitive skin.

Solutions of Surfactant in Water

• No oil phase soapless cleanser.
• Suitable for oily skin.
• Typical ingredients: surfactant, water, perfume (color, preservative).

Ingredients Causing Safety Concerns: Parabens

• Mixtures of parabens may reduce individual levels while increasing effectiveness.
• Studies in the 21st century show low potential risk of breast cancer and endocrine disruption.
• Regulations restrict paraben level in products.

Ingredients Causing Safety Concerns: Triclosan

• Used in antibacterial personal care products.
• Effectiveness in reducing bacterial counts on hands may be questioned.
• Shown to be unnecessary and may contribute to antibiotic resistance and have potential hormonal effects.
• Is under review by the FDA.

Ingredients Causing Safety Concerns: SLS

• Irritative ingredient that causes skin and mucous membrane irritation.
• Not carcinogenic but can cause skin irritation, in some cases.
• May be safe when used in short periods with rinsing..
• May not be suitable for leave-on applications.

Ingredients Causing Safety Concerns: Microbeads

• Tiny particles used in scrubs, made from natural materials or plastics.
• Can be a health concern due to their potential impact on wastewater systems.

Ingredients Including Specific Chemical Examples

• Specific chemical examples and their related uses/properties are noted where available in the provided text.

Explore the intriguing history and scientific principles behind soap and cleansers in this quiz. From ancient practices to modern formulations, test your knowledge on the advantages of synthetic soaps, historical figures involved in hygiene advancements, and the role of lather in cleaning applications.