In general, if the thumb nail protrudes is the following factors: 1. Nails are easily infected by bacteria, viruses, fungi and other undesirable factors, especially in the case of fungal infections, gray nails will appear. If the thumbnail protrudes, it is important to consider whether there is a middle nail that turns gray and becomes brittle and easy to fall off. In this case, we usually have to consider gray nail disease, which is caused by fungal infection.2. When the human body is deficient in vitamins, such as vitamin B and vitamin A, the nail cover will also be raised, and the nails will be brittle and easily folded at this time.3. In some cases of peripheral neuritis, especially diabetes combined with peripheral neurorrhaphy of the fingertips, the nails will be The nails will protrude, and accompanied by pain and itching of the nails and fingertips.