The primary reason for nails developing longitudinal ridges or splitting vertically is age, according to Mayo Clinic. These ridges that extend from the nail bed to the nail tip are generally harmless.
Nails Magazine points out that longitudinal ridging, technically known as onychorrhexis, is often exacerbated by placing the hands in alcohol or water for long periods or by stress caused to the nails from typing or playing piano. Vertical splitting of the nails is an inconvenience, but it is not a health risk. However, it is sometimes associated with other skin conditions, including eczema and psoriasis. It can also indicate an underactive thyroid gland or anemia.
There is some research to support taking biotin in order to strengthen brittle nails. Keeping nails regularly manicured diminishes the unattractive appearance of vertical splitting.