Black fingernails may be the result of a hematoma, according to Dr. Melissa Conrad Stöppler writing on MedicineNet. A hematoma is a pool of blood under fingernails that is usually the result of some type of trauma. More »

According to NHS Choices, blue fingernails are caused by low blood oxygen levels or poor circulation brought on by exposure to cold temperatures. This condition is called "peripheral cyanosis." More »

A person with a green fingernail is suffering from a condition called green nail syndrome. This infection leads to discoloration of the nails, usually referred to as chloronychia. More »

Dr. Melissa Conrad Stöppler explains on MedicineNet that arm pain stems from a number of sources including abnormalities in the skin, nerves, bones, joints, blood vessels and soft tissues of the arm. She also explains th... More » Health Conditions & Diseases

Fingernails curling is sometimes a result of the aging process, the way the minerals form once off of the nail bed, but sometimes it can be an indicator of lung problems. Sometimes fingernails curl under as a result of "... More » Beauty & Fashion Nail Care

Fingernails and toenails marked by horizontal waves or ridges are typically the result of the medical condition known as Beau's lines, according to Skinsight. An abrupt interruption of nail keratin synthesis causes the w... More »

Fingernails can grow downward as a result of a condition called nail clubbing in which the fingers grow larger, while the nails grow around and curve over the larger fingertips, explains Mayo Clinic. Health problems such... More »