Generally when a finished cosmetic product comes into contact with the skin of potential consumers, it is very unlikely that observable signs of irritation are noticed in normal use. However, the overall perception of the finished product by the consumer is an important criterion for accepting its cosmetic use. In this global perception many different parameters may play a role, some independant of the potential irritancy of ingredients, such as feeling of aesthetic nature, ease of spreading on the skin, viscosity, perfume, and color. However, the subjective perception of skin feel is closely related to the composition of the cosmetic product. Skin feel attributes, such as self-perception of dryness (feels tight, rough, and dry), or irritation (itching and burning), softness, and smoothness are easily perceived by the subjects. In most cases, the subjects are able to perceive very early on the effects of some cosmetics on the skin well before they become clinically observable or measurable by bioengineering techniques. The assessment of the self-perception of the interaction between some cosmetic ingredients with the stratum corneum is performed by means of questionnaires where several skin attributes are evaluated. Some questionnaires are designed to receive an answer Yes or No to each of the attributes, or the subject will have to rate each of the attributes on a 0 to 10 point scale.
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