Thickened and arched toenails may be caused by nail fungus, lichen planus, psoriasis and other diseases, according to different diseases can be used in different treatment methods. 1. nail fungus disease: toenail deformation thickening arch may be caused by nail fungus disease, daily need to pay attention to personal hygiene, keep local dry. Serious patients can take oral antifungal drugs as prescribed by the doctor, such as itraconazole, terbinafine, etc., with antibacterial effect. 2. Lichen planus: thickened and arched toenails may be caused by lichen planus, and patients need to pay attention to nail injuries. Patients can follow the doctor’s instructions to apply local Vitamin A cream, tazarotene and other Vitamin A drugs, can dissolve keratin. 3. Psoriasis: If psoriasis causes thickening and arching of the toenails, patients need to wear loose, comfortable and breathable shoes and socks. Patients can follow the doctor’s instructions to use topical glucocorticoid cream, such as mometasone furoate ointment, halometasone ointment, with anti-inflammatory effect. You can also take tonicin combined with long-wave ultraviolet (UVA) phototherapy, which can inhibit immune cell activation. There are many reasons that lead to toenail deformation thickening arch, it is recommended that patients go to the hospital, clear causes, standardized diagnosis and treatment.