Vertical fingernail ridges, which run from the cuticle to the tip of the nail, are harmless and usually appear as people age. Horizontal fingernail ridges, also known as "Beau's lines," can be caused by previous injury or various health conditions.
Vertical nail ridges are formed as the nail grows and are very common in people of all ages. They tend to become more pronounced with age, but they are not considered a sign of any health issues. Horizontal nail ridges, however, can be a symptom of vitamin deficiency, some health conditions and, in rare cases, arsenic poisoning. Those with concerns about ridges should seek the advice of a physician.