Nail ridging and nail brittleness are common nail problems. Ridging is a normal part of aging and can be associated with brittleness. Nail brittleness is also called onychorrhexis. It can be caused by many factors, including excessive water or soap exposure, nail polish remover, and hypothyroidism (underactive thyroid). Biotin supplements, available at health food stores, can be helpful. Daily application of a thick emollient such as plain petrolatum and certain commercially available nail conditioners can also decrease the brittleness.