Brittleness of the nails, meaning that the nails easily become cracked, chipped, split, or peeled, can be observed as a sign of aging or in response to the long-term use of nail polish or exposure to moist conditions (including frequent swimming or dishwashing).ome diseases are also associated with changes in the nails, which can include brittleness. Thin and brittle nails can be a sign of hypothyroidism, for example. The term onychoschizia refers to splitting of the fingernails as well as brittle or soft nails.