Tacalcitol is primarily used in the treatment of psoriasis, a chronic skin condition characterized by rapid skin cell growth leading to scaling and inflammation. It works by modulating skin cell proliferation and differentiation, helping to normalize the skin's growth cycle. This reduces the thickness of psoriatic plaques and alleviates symptoms such as itching and redness. Tacalcitol is often applied topically as an ointment or cream, making it a convenient option for localized treatment. It is particularly effective for mild to moderate psoriasis and is sometimes used in combination with other therapies for enhanced results. Additionally, it has a favorable safety profile with minimal systemic absorption, reducing the risk of side effects.