LIFESTYLE COSMETICS
Bitter is better: new way to soothe sensitive skin
Bernd Walzel, Anja Herrmann, Ulrike Bätz, Beatrix Senti, Tamina Shah, Stefan Bänziger – Lipoid Kosmetik ABSTRACT
Good medicine tastes bitter, said Confucius.1
Indeed, many active
pharmaceutical ingredients taste bitter, manifesting the cross-cultural believe that the bitterness of medicine is correlated with beneficial pharmacological activity. Bitter taste receptors have recently been discovered in skin. Their activation triggers the synthesis of skin barrier lipids,2-6
making
Skin sensitivity and its symptoms like redness, itching, stinging, or burning sensations, are now a top concern among consumers globally. Around 60% of the population report having some degree of skin sensitivity,9
with many
experiencing a negative impact on their quality of life.10 Increasing awareness of skin sensitivity is changing the beauty industry. According to a Mintel database search, the number of beauty and personal care products with sensitive skin claims has increased by 37% since 2018. Sensitive skin claims are used across several categories and product formats; the top category with the greatest number of sensitive skin product launches (January to December 2022) is ‘skin care’ (56%), with their subcategories ‘face/neck care’ (41%), ‘body care’ (16%), ‘face cleansers’ (15%) and ‘sun care’ (9%).
Characteristics of sensitive skin Sensitive skin is typically described as skin with regular occurrences of unpleasant sensations, such as heat, stinging, burning, itching, or tingling, but also as skin with visible changes, like redness, dryness, scaling, bumps, or hives, all caused by forms of stimulation that wouldn’t normally create this type of reaction.9 Sensitive skin does not appear the same
way for everyone. Its severity can range from moderate discomfort to severe reactions. Its frequency can fluctuate from occasional flare-ups to more persistent, daily sensitivity.
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Its underlying cause can range from genetic predisposition to physical, environmental, or chemical stimuli, or even overuse of cosmetics. Despite this great variety, all types of sensitive skin share these three key characteristics. ■ A compromised epidermal barrier. A key characteristic of sensitive skin is a compromised lipid barrier, causing disturbed skin functions, such as increased trans- epidermal water loss, dryness, or scaling. Further, a weakened stratum corneum barrier is more permeable to environmental irritants. ■ Redness and inflammation. Redness, flushing, irritation are common symptoms of sensitive skin arising from inflammatory processes, all characterized by the production and release of inflammatory cytokines, chemokines, and interleukins. ■ Sensory discomfort. Subjective, uncomfortable, sensory effects typically occur with sensitive skin. Itching, burning, stinging, or tightness are consistently present. Nerves are more responsive and have lower thresholds to environmental, physical, and chemical factors, provoking unpleasant skin sensations.
Bitter taste receptors in skin - novel cosmetic targets The database of bitter substances lists more than 1,000 compounds,11
mostly originating
from plants. Plants produce bitter-tasting substances as protection to deter herbivorous animals. Indeed, some bitter substances are poisonous, and their ingestion must be avoided, whereas others have health benefits.
them novel targets for the treatment of sensitive skin. Amaretine® (hereafter called the bittersweet complex) builds on this new knowledge by combining bitter with sweet components: bitter andrographolide from Andrographis paniculata leaves and sweet glycyrrhetinic acid from Glycyrrhiza glabra roots activate the skin’s bitter receptors and reduce inflammatory responses.7,8 Both active components are enclosed in a liposomal carrier system for optimal dermal delivery, to synergistically comfort sensitive skin. The bittersweet complex performs excellently in consumer surveys, where people with sensitive skin report a reduction in redness, itching, stinging, or burning sensations after treatment. This action was further confirmed in clinical studies, as well as in placebo controlled in vivo and in vitro studies. Finally, we could show that improving symptoms of sensitive skin measurably improves the quality of life of affected people.
For example, andrographolide, derived from the bitter-tasting herb Andrographis paniculata, is used in Ayurvedic medicine as bitter tonic. The recognition of bitter substances in the
oral cavity is mediated by bitter taste receptors belonging to the taste 2 family (TAS2R) of G-protein coupled receptors. We humans have 25 different bitter taste receptors, each specific for a different set of bitter substances. The activation of bitter taste receptors on taste receptor cells triggers an intracellular signal cascade that finally produces the sensation of bitterness.12 Apart from sensing taste, bitter taste
receptors have more physiological roles: Bitter taste receptors also exist in extra-oral tissues, for example in our digestive tract, where epithelial cells recognize bitter nutrients, or
April 2023 PERSONAL CARE
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