Atopic dermatitis (AD) is a chronic pruritic inflammatory skin disorder that is thought to be a multifactorial disease caused by both genetic and environmental factors. AD is characterized by allergic inflammation and epidermal barrier dysfunction, and excessive serine protease activity is a characteristic abnormality that affects the epidermal barrier in AD patients. The expression and activity of the serine proteases, kallikrein-related peptidases (KLKs) , are increased in the skin lesions. We reported Th2 cytokines IL-4 and IL-13 induced the expression and activity of KLK7 in epidermal keratinocytes. The serine protease inhibitors are preventive or therapeutic medicines for AD.

　Itch has been defined as an unpleasant sensation that evokes the desire to scratch. Itch is also believed to signal danger from various environmental factors or physiological abnormalities. Itch sensation is induced via nerve endings in the skin whose cell bodies are located in the dorsal root ganglia (DRG) and trigeminal ganglia. Neuronal excitation propagates to the brain through the spinal cord dorsal horn, inducing an itch sensation. Therefore, it is believed that itch hypersensitivity and chronic itch may involve abnormalities in neurotransmission or neural circuitry from skin to brain. Antihistamine-resistance and intractable itch impair quality of life (QOL) , and frequently accompany inflammatory skin conditions and systemic diseases. In some cases, intense itch impairs QOL more so than pain. Such itch is present in patients with atopic dermatitis (AD) . As first-line antipruritic therapy, antihistamines (H₁-receptor antagonists) are commonly used in treatment of AD, although it is often difficult to control the itch. This review describes present knowledge regarding mechanisms of antihistamine-resistance and intractable itch.

　Classifying primary cutaneous vasculitis has proven to be both challenging and controversial. We previously set out to establish a classification system and algorithm to diagnose vasculitis with cutaneous manifestations from a dermatological point of view based on the 1994 Chapel Hill Consensus Conference Classification and our research results with approval from the Guideline Committee of Vasculitis within the Japanese Dermatological Association (Katsuoka Group) . We recently developed a new version of the classification and algorithm for primary cutaneous vasculitis based on the 2012 Chapel Hill Consensus Conference Classification with approval from the Guideline Committee of Vasculitis within the Japanese Dermatological Association (Furukawa Group) . Cutaneous symptoms are highly noticeable, and by interpreting the cutaneous manifestations, dermatologists can ascertain the type of affected vessels. Palpable purpura is indicative of small vessel vasculitis in the upper dermis. On the other hand, livedo racemose is indicative of medium-sized vessel vasculitis in the lower dermis to subcutaneous fat. Dermatological examinations using the proposed algorithm in vasculitis patients may enable us to refine our earlier diagnostic strategies. Furthermore, we organized a Japanese committee (Kawakami Group) to make a new version of the classification and algorithm for primary cutaneous vasculitis.

　Loss-of-function mutations in filaggrin are known to be major predisposing factors for atopic dermatitis (AD) . Experiments using filaggrin-null mice demonstrated that complete filaggrin deficiency led to altered barrier integrity and enhanced sensitization. Protecting the skin barrier with a moisturizer during the neonatal period was hypothesized to prevent the development of AD and allergic sensitization. Randomized controlled trials to investigate this hypothesis were performed at the same time by two groups, in Japan and abroad, USA and UK. Both groups concluded that daily application of moisturizer during the first weeks of life reduces the risk of AD/eczema in infants. By post-hoc analysis, the Japanese group found a significant difference in the cumulative AD incidence between the high and low transepidermal water loss (TEWL) groups of the forehead. The probability without AD was lower in the high TEWL group than in the low TEWL group. The high TEWL group also exhibited a higher rate of sensitization to ovomucoid.

　A 27-year-old male visited our clinic exhibiting edema of the left hand. His history indicated that he had developed swelling of both hands approximately 6-7 times per year for the last few years. The swelling usually improved within one day. A few days before his visit, he had assembled furniture and used a hammer with his left hand. His left hand then presented with marked edema and a mild itch. There was edema on the back of the left hand and on the left fingers during his visit to our clinic. Laboratory tests indicated normal levels of complement and C1 esterase inhibitor activity. A vibration load test was carried out by vibrating the extensor surface of his left forearm for 10 minutes using a shaking, Thermo-Mixer. Marked edema with redness and slight itch appeared along the left forearm beyond the contact point of the shaking mixer. The swelling with redness around the vibration site continued for 7 hours. The pressure load test was negative and dermatography was positive. The diagnosis was vibratory angioedema (vibratory urticaria) .

　We report the case of a 52-year-old Japanese female who was diagnosed with allergic contact dermatitis due to a cosmetic rubber sponge. The patient developed marked facial swelling and erythema after applying make-up. Patch tests with the cosmetics and cosmetic rubber sponge ( as is ) were negative. However, re-testing with the sponge dipped in distilled water was positive. Further patch tests with the 2008 Japanese standard allergens resulted in positive reactions to thiuram mix and dithiocarbamate mix. Among their constituents, tetramethylthiuram monosulfide, tetraethylthiuram disulfide, and zinc diethyldithiocarbamate (ZDEC) were positive. Gas chromatography/mass spectrometry-based analysis detected ZDEC in the cosmetic rubber sponge. ZDEC was used as a vulcanization accelerator during the manufacturing process. Thus, it was assumed that the patient had been sensitive by ZDEC. In our case, a wet cosmetic sponge dipped in distilled water demonstrated a stronger reaction than a dry sponge ( as is ) . Furthermore, dipping the sponge in water revealed the same positive reaction as when the sponge was dipped in acetone and ethanol. ZDEC is minimally soluble in water ; however, we speculate that extremely small amounts of ZDEC are dissolved when the cosmetic rubber sponge is moistened with distilled water, which explains the abovementioned positive patch test results.

　A 79-year-old man was treated with ethambutol and clarithromycin for non-tuberculous mycobacteriosis and later started taking sitafloxacin because of exacerbation of his respiratory condition. One month later, he developed erythema on the face, neck and dorsal aspects of both hands the day after working in strong sunlight. Sitafloxacin showed a positive reaction in a photo-drug test with UVA irradiation dose of less than 1.5 J/cm². A diagnosis of photosensitive drug eruption induced by sitafloxacin was made.

　Toxic epidermal necrolysis (TEN) , Stevens-Johnson syndrome (SJS) , and drug-induced hypersensitivity syndrome (DiHS) are life-threatening severe cutaneous adverse reactions (SCARs) . Corticosteroids have been used for such cases in Japan, and recommended as first-line treatment in the 2016 Japanese guidelines for the treatment of SJS/TEN. We have successfully treated TEN, SJS, and DiHS cases using corticosteroid pulse therapy in the early phase of the disease. Rapid improvement was observed in clinical symptoms without side effects, such as infections or sequelae such as visual disorders. We herein present each case of TEN, SJS, and DiHS with a review of corticosteroid pulse therapy in the early phase of SCARs.