Lotions: Composition and Applications

Study Notes

Lotions are liquid preparations containing solid materials for external application to the skin.
Used for treating local skin conditions like inflammation, acne, infections (bacterial, fungal, viral, and parasitic).
Also used as washes, gargles, and solutions for urethral or vaginal irrigation.
Most lotions are suspensions or emulsions, requiring a "shake before use" label.
Lotions are for external use only.

Therapeutic Agents: Medications for specific skin conditions.
Alcohol: Acts as a coolant due to evaporation and as a co-solvent.
Humectants: Retain moisture on the skin. Glycerol is a common example.
Vehicle: Purified water.
Preservatives: Prevent microbial growth, examples include:
- Phenol (0.2-0.5%)
- Chlorocresol (0.075-0.12%)
- Benzoic acid (0.1-0.3%)
Stabilizers: Help keep suspended therapeutic agents stable.

Medicinal Lotions:
- Antiseptic and germicidal properties.
- Treatment of skin diseases.
- Cooling and mild anesthetic effect for skin irritation.
Cosmetic Lotions:
- Applied to hair, scalp, face, and hands.
- Widely used as sunblock preparations.

Sunlight contains visible light, infrared (IR) rays, and ultraviolet (UV) radiation.
IR rays produce a sensation of heat.
UV radiation is responsible for therapeutic and toxic effects on the skin.
UV can penetrate the skin causing degeneration.
Histidine is liberated and converted to histamine, leading to:
- Dilation of blood vessels.
- Local irritation with severe itching and burning.
Excessive UV exposure leads to increased melanin synthesis as a protective measure against UV radiation.

Adding alcohol to a lotion hastens drying and increases cooling effect.
Adding glycerol keeps the skin moist.
Highly viscous suspending agents like gum tragacanth are not ideal due to stickiness.
For hydrophobic substances (sulfur, Mg. stearate), a wetting agent (glycerin or mineral oil) should be added to aid in wetting with water.