Itching under the nail cap is considered to be inguinitis, onychomycosis, psoriasis, etc., which needs to be treated with medication, physical and surgical options. 1. Nail groin infection: often due to bacterial infection caused by tiny puncture wounds, contusion, reverse peeling or cutting nails too deep, etc. If the inflammation invades under the nail, there will be subnail abscess, causing pain and itching, resulting in itchy under the fingernail cover. You can take amoxicillin capsules, cefixime capsules and other antibiotic drugs, if the condition is serious, you can also do abscess drainage and nail extraction treatment. 2. Onychomycosis: It is triggered by fungal infections such as Trichophyton rubrum and Trichophyton mustelii, which can lead to abnormalities of the nails, such as clouding, discoloration, and shedding, and also cause itching under the nails. You can apply topical amorolfine hydrochloride application, cyclopamine cream, etc., and take anti-fungal drugs such as terbinafine hydrochloride tablets and itraconazole capsules. 3. Psoriasis nail: the onset of psoriasis is related to heredity and environment, which will lead to scaly erythema of the skin, and if the nails are involved, it mainly manifests as loss of luster, thickening, pitting on the nail surface, nail peeling, etc., and also causes itching underneath the nail cover. You can apply hydrocortisone butyrate cream, mometasone furoate cream and other drugs, and with photochemotherapy and excimer laser and other physical therapy. Itchy nails can also be seen in subnail melanoma, onychomatous nevus, etc., need to do the corresponding identification, it is recommended to go to the hospital in a timely manner, complete further examination, and comply with the doctor’s instructions to use medication.