Type 2 immunity, illustrated by T helper 2 lymphocytes (Th2) and downstream cytokines (IL-4, IL-13, IL-31) as well as group 2 innate lymphoid cells (ILC2), is important in host defense and wound healing. 1 The hallmark of type 2 inflammation is eosinophilia and/or high IgE counts and is best recognized in atopic diathesis. Persistent eosinophilia, such as seen in hypereosinophilic syndromes, leads to fibrosis and hence therapeutic Type 2 inhibition in fibrotic diseases is of high interest. Furthermore, as demonstrated in cutaneous T cell lymphoma, advanced disease is characterized by Th1 to Th2 switch allowing cancer progression and immunosuppression. Development of targeted monoclonal antibodies against IL-4Rα (eg, dupilumab) led to a paradigm shift for the treatment of atopic dermatitis (AD) and stimulated research to better understand the role of Type 2 inflammation in other skin conditions. In this review, we summarize up to date knowledge on the role of Type 2 inflammation in skin diseases other than AD and highlight whether the use of Type 2 targeted therapies has been documented or is being investigated in clinical trials. This manuscript reviews the role of Type 2 inflammation in dermatitis, neurodermatitis, IgE-mediated dermatoses (eg, bullous pemphigoid, chronic spontaneous urticaria), sclerodermoid conditions and skin neoplasms.

Prurigo pigmentosa (PP) is an uncommon inflammatory dermatosis first described in 1971. It is characterized by recurrent crops of pruritic erythematous papulovesicles that resolve with a macular reticulated hyperpigmentation. The exact etiology is yet to be determined, however with the expanded application of the ketogenic diet (KD) in recent years, conditions accompanied with ketosis are more commonly being described in association with PP. Antibiotics as well as resolution of ketosis can effectively treat the dermatitis. Given the publicity and growing popularity of the ketogenic diet and numerous references to the “Keto‐Rash” on social media, we reviewed the KD‐induced PP cases to raise awareness of this increasingly recognized entity and provide an update to clinicians, particularly dermatologists, regarding this possible side effect of KD.

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