Sunscreens

Definition of Sunscreens:

• Sunscreens are topical formulations that protect the skin from harmful UV radiation.

Formulation Goals:

• Protection: Provide broad-spectrum protection against UV-A and UV-B radiation.
• Aesthetic Acceptability: Non-greasy, non-whitening, and cosmetically elegant.
• Stability: Maintain efficacy upon exposure to light, heat, and over time.
• Skin Compatibility: Minimize irritation and allergic reactions.

Types of Sunscreens: Physical vs. Chemical:

1. Physical (Mineral) Sunscreens

   • Active Ingredients: Titanium dioxide, zinc oxide.
   • Mode of Action: Reflect or scatter UV light.
   • Challenges: White cast; micronized or nano-sized particles improve appearance.

2. Chemical Sunscreens

   • Active Ingredients: Avobenzone (UV-A), octinoxate, octocrylene (UV-B).
   • Mode of Action: Absorb UV radiation, dissipate as heat.
   • Challenges: Photodegradation; stabilized with antioxidants and UV absorbers.

Key Ingredients:

1. UV Filters:
   • Physical Filters: Reflect UV rays (e.g., titanium dioxide, zinc oxide).
   • Chemical Filters: Absorb UV rays (e.g., avobenzone, oxybenzone).
2. Emollients: Provide moisturizing properties (e.g., shea butter, glycerin).
3. Preservatives: Prevent microbial growth.
4. Antioxidants: Protect skin and stabilize the product.

Processing/Preparation Methods:

1. Phase Preparation:
   • Oil Phase: Heat lipophilic ingredients (oil-soluble UV filters, emollients) to 70–80°C.
   • Aqueous Phase: Dissolve water-soluble ingredients (humectants, preservatives) with controlled heating.
2. Emulsification: Combine oil and water phases under high-shear mixing at a common temperature to form an emulsion.
3. Active Ingredients:
   • Chemical Sunscreens: Add UV filters to the oil phase or encapsulate for stability.
   • Physical Sunscreens: Carefully disperse titanium dioxide or zinc oxide to avoid clumping.
4. Cooling and Homogenization: Gradually cool while stirring to stabilize the emulsion.
5. Final Adjustments: Add heat-sensitive ingredients, adjust pH, and perform a final homogenization.
6. Packaging: Fill into airless pump bottles or tubes to prevent oxidation and contamination.

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