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Papers: 10 Aug 2019 - 16 Aug 2019


2019 Dec




Itch sensitization? A systematic review of studies using quantitative sensory testing in patients with chronic itch.


van Laarhoven A, Marker JB, Elberling J, Yosipovitch G, Arendt-Nielsen L, Andersen HH
Pain. 2019 Dec; 160(12):2661-2678.
PMID: 31408048.


As well-established for patients with chronic pain, patients suffering from chronic itch also exhibit signs of peripheral and central sensitization. This has been linked to parallel neuroplastic sensitization processes. However, for chronic itch, sensitization has not yet been systematically assessed, studied, and hence validated. This review (Prospero CRD42016043002) summarizes and meta-analytically evaluates whether sensory aberrations including sensitization for itch occur in chronic itch.Databases PubMed, Embase, and Cochrane Library were searched for studies investigating somatosensory sensitivity assessment by quantitative sensory testing stimuli, including experimental cutaneous chemical pruritic provocations, in patients with chronic itch from skin-/neurological conditions and compared with healthy controls. Outcomes were extracted for lesional and non-lesional skin and risk of biases were assessed. Meta-analyses were performed when sufficient quantitative data were available.Of 4,667 identified papers, 46 were included and 25 were eligible for meta-analyses. Patients (66% atopic dermatitis) were found more sensitive than the controls to histamine-evoked itch in lesional skin (SMD: 0.66 [CI: 0.16,1.15]), but not non-lesionally (SMD: -0.26 [CI: -0.58;0.06]). Cowhage did not evoke more itch in non-lesional skin of patients as compared to the controls (SMD: 0.38 [CI: -0.04,0.81]). For numerous other chemical provocations as well as for mechanical, thermal, and electrical stimulation paradigms, results were ambiguous or based on few studies.Patients with chronic itch are only robustly sensitized to various chemical pruritic stimuli when applied lesionally. More studies on somatosensory aberrations in chronic itch conditions other than atopic dermatitis are needed to establish whether sensitization is robustly present across chronic itch conditions.