Oral lichen planus (OLP) is a chronic inflammatory disease that affects the lining of the mouth and may cause pain, burning sensations, and discomfort. Some patients also report changes in their ability to taste different flavors.

The aim of this study is to compare two commonly used treatments for OLP: photodynamic therapy (PDT) and topical corticosteroids. PDT is a light-based treatment that uses a special gel applied to the affected areas, followed by illumination with a medical light device. Topical corticosteroids are anti-inflammatory medications applied directly to the lesions.

Participants in this study are randomly assigned to receive one of these two treatments. Before starting therapy and immediately after its completion, patients undergo a simple taste test using special strips that assess the ability to recognize sweet, sour, salty, and bitter tastes. In addition, the size of oral lesions and the intensity of symptoms such as pain or burning are evaluated.

The results of this study may help to better understand how different treatments for oral lichen planus affect taste perception and overall patient well-being, and may support the selection of the most appropriate therapy in clinical practice.

Oral lichen planus (OLP) is a chronic inflammatory disease of the oral mucosa, frequently associated with pain, burning sensations, and impaired quality of life. Alterations in gustatory function have also been reported in patients with OLP; however, the impact of different therapeutic approaches on taste perception remains insufficiently investigated.

The aim of this randomized clinical trial is to evaluate and compare the effects of ALA (5-aminolevulonic acid) -based photodynamic therapy (PDT) and topical corticosteroid therapy (CT) on gustatory function in patients with clinically and histologically confirmed OLP.

Participants are randomly allocated to one of two parallel treatment groups: (1) ALA-PDT using a 5% 5-aminolevulinic acid mucoadhesive emulgel followed by irradiation with a 630 nm LED light source, administered in five weekly sessions; or (2) topical corticosteroid therapy with clobetasol propionate applied twice daily for two weeks.

Gustatory function is assessed using standardized taste strips, evaluating sweet(0-4), sour(0-4), salty(0-4), and bitter (0-4) taste perception, as well as total taste score (0-16), before treatment initiation and immediately after therapy completion. Secondary outcomes include changes in lesion size and subjective symptom severity assessed using the Visual Analog Scale (VAS) (0-10).

This study aims to provide evidence on the comparative effectiveness of PDT and topical corticosteroids in modulating taste perception and clinical outcomes in patients with OLP, thereby supporting evidence-based therapeutic decision-making.

Inclusion Criteria:

• age 18 years or older
• clinically and histologically confirmed diagnosis of oral lichen planus

Exclusion Criteria:

• pregnancy or lactation presence of systemic diseases, including dermatologic diseases, oncologic diseases, or severe liver disorders known allergies use of immunomodulatory or immunosuppressive drugs use of antidepressants use of bone anti-metabolites photosensitivity allergy to the components of the photosensitizer treatment for oral lichen planus within the previous 6 months inability to attend follow-up visits presence of oral lesions other than oral lichen planus

Outcome assessors and laboratory personnel were blinded to group allocation. Due to the nature of the interventions (photodynamic therapy with 5-aminolevulonic acid (ALA-PDT) vs topical corticosteroids (CT)), participants and treating clinicians were not blinded.