Hollow nails are considered to be caused by onychomycosis, psoriasis, pyogenic granuloma, etc. Medication, physical therapy, surgery, etc. are needed. 1. Onychomycosis: Onychomycosis is caused by fungal infection, which leads to thickening, separation, discoloration and buckling of nails, and can also lead to nail cavities. It can be treated by local application of drugs such as Amorolfine Hydrochloride, Cyclopiazide cream and taking anti-fungal drugs such as Terbinafine Hydrochloride tablets and Itraconazole capsules. 2. Psoriasis: The causes of psoriasis are related to heredity, immune abnormality, environment, etc. If it involves the nail, it can cause nail cavities, and plaques and silvery-white scales will appear on the skin. You can take methotrexate tablets, cyclosporine soft capsules and other drugs as prescribed by the doctor, which can control the development of the disease, and you can also choose photochemotherapy, excimer laser and other physical therapy. 3. Purulent granuloma: Purulent granuloma is mostly caused by trauma, which leads to overgrowth of granulation tissue under the nail, causing nail cavities. You need to take anti-infective drugs, such as amoxicillin capsules, cefixime capsules, etc. In serious cases, you need to do nail extraction treatment, and then remove the granuloma under the nail. Nail cavities can also be seen in herpetic epidermolysis bullosa, contact dermatitis, etc. It is recommended to go to the dermatology department of the hospital, according to the cause of the symptomatic treatment, do not blindly choose drugs. All of the above drugs should be used under the guidance of a doctor.