With the increasing environmental pollution and mental stress, the incidence of sensitive skin is gradually increasing and is receiving more and more attention. In order to improve the understanding of sensitive skin and standardize the diagnosis and treatment behavior, the Dermatology and Aesthetics Group of the Chinese Medical Association, the Aesthetics Group of the Dermatologists Branch of the Chinese Medical Association, and the Photomedicine and Skin Barrier Group of the Dermatology Branch of the Chinese Society of Integrative Medicine have formulated the Expert Consensus on the Diagnosis and Treatment of Sensitive Skin in China. So, what is sensitive skin? Sensitive skin (sensitive skIn, SS) refers to a state of hyperreactivity of the skin under physiological or pathological conditions, mainly on the face, which is clinically manifested by subjective symptoms such as burning, itching, pruritus and tightness of the skin when stimulated by physical, chemical and mental factors, with or without objective signs such as erythema, scaling and capillary dilation. The causes of sensitive skin are complex. Individual factors include genetics, age, gender, hormone levels and mental factors. Recent studies have shown that sensitive skin is genetically related, with a higher incidence in young people than in older people, and in women than in men. Mental stress can reflexively cause the release of neurohypophyseal peptides, triggering sensitive skin. External factors The following factors can trigger or aggravate sensitive skin: (1) physical factors: such as seasonal changes, temperature changes, sun exposure, etc.; (2) chemical factors: such as cosmetics, cleaning products, disinfection products, air pollutants, etc.; (3) medical factors: such as topical stimulant drugs, long-term topical glucocorticoids, certain laser treatments, etc. About 66% of female patients with atopic dermatitis and 57% of patients with rosacea have skin sensitivity. *The scope of this consensus does not include sensitive skin caused by skin diseases. 2. Mechanism of occurrence Current research suggests that the occurrence of sensitive skin is a complex process involving skin barrier – neurovascular – immune inflammation. The interaction of intrinsic and extrinsic factors leads to impairment of skin barrier function, resulting in an increase in sensory neurotransmitter signals, leading to increased skin reactivity to external stimuli and triggering an immune inflammatory response in the skin. Damage to the skin barrier function The incomplete structure of the stratum corneum and the imbalance of lipid content between epidermal cells in sensitive skin can lead to a decrease in ceramide content. Skin physiological tests show that the transepidermal water loss (TEWL) increases and the water content of the stratum corneum decreases in sensitive skin, both indicating impaired barrier function. Ambient temperature can trigger or exacerbate sensitive skin because low or high skin surface temperatures (below 34°C or above 42°C) can delay skin barrier repair. Skin sensory nerve dysfunction is caused by a combination of reduced protection of skin nerve endings, increased nerve fiber density, and increased responsiveness of sensory nerves, which is associated with activation of the transientreceptor potential (TRP) family. The transient receptor potential vanilloid 1 (TRPV1) can be activated by physiological or sub-physiological temperature (below the normal activation temperature of TRPV1), which can cause burning, tingling and pruritus in sensitive skin. TRPV1 is often referred to as the capsaicin receptor because of its susceptibility to activation by capsaicin. The occurrence of sensitive skin is not only associated with the abnormal peripheral nerve function described above, but also with altered central nerve function. Increased vascular reactivity TRPV1 is expressed in mast cells and keratinocytes, and endothelin (ET) is secreted by endothelial cells and mast cells and induces mast cell degranulation leading to neurogenic inflammation. This increases vascular reactivity and triggers vasodilation. The activation of TRPV1 not only promotes the release of local cutaneous neurotransmitter substance P, vasoactive intestinal peptide, neurohypophyseal peptide and tryptophan, but also leads to the release of IL-23 and IL-31 from keratinocytes and mast cells near sensory nerve endings, and activates antigen-presenting cells and T cells, thus triggering cutaneous immune and inflammatory reactions. 3.Clinical manifestations Subjective symptoms Usually, the skin has different degrees of burning, stinging, itching and tightness after physical, chemical and mental stimulation, which lasts for several minutes or even hours, and often cannot tolerate ordinary skin care products. Objective signs The appearance of sensitive skin is mostly normal, but a few people may have flaky or diffuse flushing, erythema, capillary dilation, which may be accompanied by dryness and fine scaling. 4.Assessment methods Currently, there are three main methods for assessing sensitive skin: Subjective assessment Firstly, respondents are asked to self-assess their skin sensitivity based on whether their skin is prone to subjective symptoms such as burning, tingling, itching and tightness when stimulated by triggering factors, and to conclude whether they have sensitive skin. Possible triggers: (1) physical factors: such as seasonal changes, temperature changes, sun exposure; (2) chemical factors: such as cosmetics, cleaning products, disinfection products, irritating topical drugs such as retinoic acid, environmental pollutants (such as haze, dust, exhaust fumes); (3) mental factors: such as anxiety, depression, etc. Semi-subjective assessment Irritation test as a semi-subjective method has now been widely used in the determination of sensitive skin, commonly used are lactic acid tingling test, capsaicin test, etc. The lactic acid tingling test is one of the more widely used evaluation methods, the most classic of which is the application method: 50 μL of 10% lactic acid solution is applied to the nasolabial folds and either cheek at room temperature, and the subject is asked about his or her self-perceived symptoms at 2.5 min and 5 min, respectively, and scored on a 4-point scale (0 being no tingling sensation, 1 being mild tingling, 2 being moderate tingling, and 3 being severe tingling ). The two scores were then summed, and a total score of ≥3 was considered positive for lactic acid stinging response. Capsaicin test is commonly used to evaluate sensory neuropathic sensitivity of the skin. Two layers of filter paper with a diameter of 0.8 cm were placed about 1 cm outside the nasolabial fold on one side and either cheek, and 50 μL of capsaicin at a concentration of 0.1‰ was placed on the filter paper and the subject was asked about the sensation (1 being barely perceptible, 2 being mildly perceptible, 3 being moderately perceptible, 4 being severely perceptible, and 5 being painful). A subject was considered positive if the burning pain sensation lasted >30S and the degree was ≥3. Objective assessment Objective assessment mainly applies non-invasive skin physiological index tests, which can better reflect the severity of sensitive skin or treatment effect. Commonly used quantitative indicators are: (1) transepidermal water loss rate: indirectly reflecting the barrier function of skin stratum corneum, the value is often increased in sensitive skin; (2 ) stratum corneum water content: the value is often decreased in sensitive skin; (3) pH: pH value is often increased in sensitive skin; (4) sebum: mainly detecting the sebum content from sebaceous glands, the amount of sebum is often decreased in sensitive skin; (5) skin erythema index: Application of skin chromaticity spectrophotometer can indirectly determine the degree of skin surface erythema, sensitive skin erythema-related parameters are often significantly higher; (6) local blood flow velocity and blood flow distribution histogram: the application of color Doppler flow meter to determine the local blood flow condition, sensitive skin often has local blood flow obstruction performance. 5.Diagnosis and differential diagnosis The diagnosis should meet the primary conditions and secondary conditions for reference. The main conditions include the following: ① subjective symptoms: burning, stinging, itching and tightness when the skin is stimulated by physical, chemical and mental factors; ② exclusion of primary diseases that may be associated with sensitive skin such as rosacea, seborrheic dermatitis, hormone dependent dermatitis, contact dermatitis, atopic dermatitis and swelling lupus erythematosus. Secondary conditions Include the following: ① signs: skin flushing, erythema, capillary dilation and scaling; ② subjective assessment suggesting sensitive skin; ③ semi-subjective assessment: lactic acid irritation test score ≥ 3; or capsaicin test ≥ 3; ④ non-invasive skin physiological index test suggesting abnormal changes in skin barrier function. 6.Treatment The overall principle is to strengthen health education, promote skin barrier repair, reduce neurovascular hyperreactivity and control inflammatory response, etc., in order to improve the tolerance of the skin. Health education Sensitive skin is very prone to recurrence, so psychological guidance and health education are very important. Various triggers should be avoided as much as possible, such as sun exposure, consumption of spicy foods, alcohol consumption, mood swings, confined hot environments, etc., and abuse of cosmetics should be avoided. Regular treatment and follow up, cooperate with treatment under the guidance of doctors, keep patience and build up confidence so that the skin can be maintained in a good condition. Reasonable skin care Repairing the damaged skin barrier is an important measure to treat sensitive skin. Reasonable skin care should follow the principles of gentle cleansing, soothing and moisturizing, and strict sun protection. It is advisable to use medical skin care products that have been tested and clinically proven to have good safety. Exfoliating products are forbidden, warm water should be used for cleansing, and the number of cleansing sessions per day should not be too many. Use medical skin care products with skin barrier repair effect according to seasonal changes. Physiotherapy Cold spray, cold film and cold ultra For patients sensitive to thermal stimulation, the physical effect of low temperature can be used to shrink the dilated capillaries to reduce inflammation. Red light and yellow light Red light has anti-inflammatory and promotes skin barrier repair; yellow light promotes cell metabolism and reduces peripheral nerve fiber excitability. It provides relief and treatment for various symptoms of sensitive skin. Intense pulsed light and radio frequency Intense pulsed light can promote the repair of skin barrier function and relieve skin sensitivity symptoms by closing dilated capillaries through thermal coagulation and photomodulation of epidermal cells. Radiofrequency can stimulate dermal type I and III collagen proliferation and improve the tolerance of the skin. Medication For severe symptoms, medication can be used as appropriate. For those with significant burning, stinging, itching and tightness, anti-inflammatory and antihistamine medication can be chosen. For those with anxiety and depression, anti-anxiety and depression medication can be used as appropriate.