From infestation to inflammation: the link between scabies and Th2-mediated skin diseases explored by a global population-based study

Scabies is a parasitic infestation known to elicit a strong Th2 immune response. While this immune profile overlaps with various Th2-mediated inflammatory skin diseases (T2ISDs), the potential of scabies to act as a trigger for these conditions remains poorly defined. To assess whether scabies is associated with an increased risk of developing T2ISDs, including atopic dermatitis (AD), bullous pemphigoid (BP), prurigo nodularis (PN), chronic spontaneous urticaria (CSU), Wells syndrome (WS), hypereosinophilic syndrome (HES), and DRESS syndrome. This global, population-based, retrospective cohort study utilized data from the TriNetX platform. Patients diagnosed with scabies were matched 1:1 with controls based on demographics and comorbidities using propensity score matching. The incidence of T2ISDs was analyzed and stratified by time (0–1, 1–2, and 2–4 years after infestation). Hazard ratios (HRs) were calculated using Cox proportional hazards models. The study included 88,668 patients with scabies and 88,668 matched controls. Scabies was significantly associated with an increased risk of AD (HR 1.72), BP (HR 8.40), PN (HR 1.19), and CSU (HR 1.73). These risks were highest in the first year post-infestation, but remained statistically significant even in the second year for AD, BP, and CSU. The risk of HES was elevated only in the first year (HR 4.99), while no significant association was found with WS or DRESS syndrome. Risk patterns varied by sex and age, with stronger associations seen in males for AD and CSU, and in females for BP and PN. Scabies is a significant short-term risk factor for developing multiple T2ISDs, particularly within the first two years following infestation. These findings highlight the importance of monitoring scabies patients for emerging inflammatory dermatoses and suggest that scabies may be associated with disease onset in predisposed individuals.