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Consumer Perspective—Seasonal Cleansing
By: Katerina Steventon, PhD, of FaceWorkshops
Posted: August 15, 2012, from the August 2012 issue of Cosmetics & Toiletries.
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Th effect of environmental conditions on the skin changes with geographic location and season. Exposure to hot weather or climate induces sweating, sebum excretion and open pores, increased blood flow and vasodilation. Higher skin temperature increases sebum excretion in the range of 10% per 1°C;2 exposure to cold climate oft en has the opposite effect.
The stratum corneum is a biosensor and its barrier function responds adaptively to the external environment. In terms of diff erent climates, humidity and temperature play an important role. For example, consumers living in dry climates like Arizona have a stronger barrier function and less dry skin, compared with those living in humid climates such as New York. This is due to increased ceramide and desquamatory enzyme levels.3 Also, in animal models, barrier function is enhanced by prolonged exposure to a dry environment due to higher epidermal lipid synthesis and increased lamellar body production. In contrast, after the skin adapts to high humidity, there is a delay in barrier recovery due to the diminished capacity of the skin to respond to external challenges.4
In terms of seasonal change, during winter months, there is a significant reduction in stratum corneum ceramides, cholesterol and fatty acids5 and also in the natural moisturizing factor (NMF); in particular, potassium and lactate levels, with a concomitant increase in pH and stratum corneum stiffness.6 These changes often lead to a weaker barrier function and precipitate the “dry skin cycle”.7 In summer, cleansing with harsh and foaming facial cleansers can potentially damage the skin barrier in a humid environment. Protecting the skin barrier function is very important when living or traveling to exotic destinations; especially for dry, sensitive skin types or skin types prone to acne and rosacea. While US research indicates that rosacea shows no significant seasonal variation,8 its increase with rising temperature has been found in the UK9 and Peru;10 empirically, central heating, air-conditioning and sun worsen the condition.
Skin Type Considerations
The face is an anatomical site with lower barrier function and high activity of sebaceous glands, compared with the rest of the body. Sebum-derived unsaturated free fatty acids can irritate the skin, induce parakeratosis and epidermal hyperplasia,11 promoting comedone formation and the onset of acne. Gentle cleansing to remove the excess sebum is recommended for acne-prone skin, and non-alkaline, non-irritating facial washes based on cetyl alcohol and propylene glycol have been shown to improve rosacea with high tolerability.12
More than 40–50% of women in the USA, Europe and Japan report they have sensitive skin, with an increase in reports during the summer rather than in winter.13 Sensitivity is defined as abnormal sub-clinical sensory response to skin care such as stinging, itching and burning in the absence of visible signs of skin irritation.14 Sensitive skin typically is associated with skin dryness, reduced sebum excretion and lipid content and low skin barrier function and pH. Sensitive skin also shows higher vasodilation and increased penetration of ingredients due to barrier impairment, a significant decrease of alkali resistance, and enhanced immune response.