Sunscreen Emulsions
Emulsions Advantages :
Good performance in each of the important areas
- Facilitate incorporation of sunscreen active agents, which are usually oils that can be easily emulsified
- Can be prepared contain large percentage of water (more cost effective vehicle)
- Cosmetically desirable vehicles (give skin smooth, silky, without being greasy)
- Can accommodate a wide variety of raw materials
- Thermodynamically unstable
- Eventually separate
- Present a perfect medium for microbial contamination and require preservatives
Water in Oil (W/O)
- Better vehicle
- Can be design as water resistant sunscreen and provide greater efficacy (higher SPF) for the same concentration as O/W emulsions.
- Most sunscreens were soluble in the oil phase, that’s why in W/O emulsions the oil phase is continuous and when applied in the skin, there is no need for agglomeration to occur. A a result a very uniform sunscreen is produced during spreading, a long with a high SPF
Oil Advantages :
Generally well accepted
- Easy to formulate and easy to apply to the skin spreading quickly and uniformly to cover a large surface area
- There is only one phase that’s why it has excellent product stability
- Most sunscreen active agent are lipoidal in nature, they are soluble in the oils employed. Because of this, manufacturing process are more straightforward than the emulsion
- Can be prepared in room temperature
- Thin and transparent sunscreen film, which will have a lower SPF
- Poor performance by looking at the interactions between sunscreen (nonpolar ester) and the nonpolar oils vehicle (mineral oil). Nonpolar oil can cause the position of the UV curves to shift to shorter wavelength
- The solubility parameter (stickiness/cohesiveness) determines orientation of the sunscreen within oil
- Sunscreen oils are expensive system since the anhydrous oil system there is no water to lower the cost of expensive raw material
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