You can develop either horizontal or vertical ridges in your nails. Vertical ridges are common and aren't generally a sign of an underlying illness. The vertical ridge extends to the tip of your finger nail from the base of your fingernail typically in a regular, orderly fashion and becomes more prominent with age. Horizontal ridges can be an indication of a medical condition. One kind of horizontal nail ridge that does announce the presence of an illness is called Beau's lines.
Beau's lines are deeply grooved horizontal ridges. The nail may be a little bit dark in appearance when you see Beau's lines, which are caused by certain medicines, malnutrition, diabetes and other metabolic disorders or injury to the nail bed. A Beau's line pops up when the growth of the nail has been stopped because of a medical problem. If you have this kind of ridge in your thumb nail or any nail, see your doctor.
Other Reasons for Horizontal Ridges
Nail ridges that are horizontal can also develop due to the interruption of nail growth caused by damage to the nail matrix or your nutritional status. A horizontal nail ridge can be an indication of arsenic poisoning.
If you are iron deficient or anaemic you may develop ridges on your thumb nails or other nails. If you are anaemic, your fingernails may become misshapen. This is called koilonychias. The nail will also be thin, have raised ridges and curve inward. Iron deficiency can occur if you've lost too much blood, have too little iron in your diet or your body absorbs iron poorly.
Ram's Horn Nail
Ram's horn nail, or onychogryposis, results in nail ridges and increases the curvature of the nail. This generally occurs on the big toe nail but it can happen to your fingernails. This type of nail grows more quickly on one side than the other and is hard to cut.
Stress or Vitamin Deficiency
Ridges in your nails can indicate stress. If you have a vitamin B deficiency this can cause ridges to appear in your nails.
Leaky Gut Syndrome
Ridges can appear on your thumb and other nails if you have leaky gut syndrome, according to Dr. Walt Stoll. When ridges appear, this can mean that your body is not absorbing minerals as it should. This is a debilitating condition that many times goes undiagnosed. This condition, which is also referred to as increased intestinal permeability, occurs when there has been damage done to the intestinal lining. When the lining is damaged it can't protect the interior or your body, filtering what is needed and what isn't. As a result, toxins leak out of the intestine into the blood stream, which causes chronic inflammation, gastrointestinal problems, gas, cramps, fatigue, joint pain and bloating as well as ridges in the nails.