The association between skin allergy testing and oral squamous cell carcinoma in oral lichen planus: a retrospective cohort study.

There is a reported association between oral contact allergy and oral lichen planus (OLP). Likewise oral squamous cell carcinoma (oSCC) is associated with OLP. It is hypothesized that chronic inflammation may contribute to oSCC risk. Ostensibly, we hypothesized that allergy testing positivity may increase inflammation and thus may be associated with oSCC in OLP. As a secondary objective, we assessed oSCC prevalence in OLP, allergen prevalence in OLP, and associations between allergy testing and OLP phenotype. To do this, we performed a retrospective cohort evaluation of OLP patients seen at the University of Utah from 2015 to 2022. Odds of oSCC occurrence by allergy testing status, clinical/demographic factors and asssociations between allergy testing and OLP phenotype were assessed using univariable and multivariable logistic regression. The prevalence of oSCC and allergy testing (patch + scratch testing) results were summarized descriptively. OLP diagnoses were confirmed by our OLP-specialized clinicians, and/or histologic assessment. Allergy testing was performed by two specialized dermatologists. oSCC diagnosis was identified via chart review and histologic data. Among 587 OLP patients identified, 133 were allergy tested and 77.4% were positive (52.4% metals, 55.3% flavorings/fragrances, 47.6% preservatives). Of those with a positive allergy test, 10 (25.6%) developed oSCC compared with 2 (5.1%) of patients with a negative allergy test. There was insufficient evidence to support an association between allergy positivity and oSCC (OR = 1.55, 95% CI 0.76-3.15). A higher percent of symptomatic visits was the only other clinical and/or demographic factor associated with oSCC occurrence (median 87.5% vs. 66.7%, p = 0.03). Of the OLP disease characteristics assessed (mouth area involved, extent of disease involvement, erosive subtype, etc.), only OLP involving the gingiva was associated with positive allergy testing (OR = 2.54,1.11-5.81). These data suggest that allergy test positivity may not be associated with oSCC. However, it was associated with more pervasive symptomatology, suggesting a possible association with more severe or recalcitrant disease.