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Why Sun Protection Is Required And The Ingredients Effective

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1. Introduction

There have been significant changes in moisturisers over recent years and ones that have SPF claims are proving to be very popular (figure 1) due to the great increase of skin cancers cases that have been observed worldwide in fair-skinned populations since the early 1970s. This is strongly linked with personal behaviour in regards to sun exposure and its ultraviolet (UV) component, and also to do with society’s views that tanning is attractive and healthy (1).
When sunlight goes through the atmosphere, all UVC and approximately 90% of UVB radiation is absorbed by the ozone layer, water vapour, carbon dioxide and oxygen. UVA radiation is less affected by the atmosphere; consequently, the UV radiation reaching the
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Keratinocytes are the most abundant cell type of the epidermis. They are of importance as they produce the structural protein keratin by the process of differentiation throughout the layers of the epidermis (6). The epidermis is organised into four distinct layers - the stratum basale, stratum spinosum, stratum granulosum and the stratum corneum (SC) (Figure 2) (7).

Figure 2. Cross section of the epidermis (7).

The (SC), is the outermost layer of the epidermis and plays a key role in maintaining skin hydration in 3 principle ways (5):
• By acting as a semi-permeable barrier.
• Providing a tortuous pathway, slowing diffusion and water loss.
By containing Natural Moisturising Factor (NMF) in corneocytes – this consists of hygroscopic humectants with the ability to retain and draw water from the environment to the SC, aiding tissue pliability.
If any of these factors are disrupted and composition of the SC changes, skin diseases may result. Humectant, emollient and occlusive containing moisturisers have been shown to increase the level of skin hydration and improve barrier function and are commonly used in combating dry skin (2). Sun filters or absorbers such as Titanium Dioxide, Zinc Oxide, Octocryalene for example, are used to prevent skin ageing caused by over exposure to UV. Different combinations of these ingredients are thought to
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