The condition of nails can signal underlying medical conditions.
Nails are made of keratin, which is also found in hair. The purpose of these body parts is to scratch, protect tissues, and to also give clues about overall health. They can warn about infection, diseases, and malnutrition. They are comprised of 6 parts. The most visible part is the hard plate. The folds are the skin around the plate. The bed is the skin area underneath the plate. The part that looks like a white crescent moon is the lunula. It is located under the plate at the base. The cuticle is the tissue that overlaps the nail at the base. Nails grow from the matrix, “an area under the protective cuticle at the base of the nail bed”.1
Normal aging, injuries, and infections can cause abnormalities in nails. A “washboard nail” may develop from rubbing or picking the skin behind the nail. They can become brittle just from overuse of polish or too much moisture. Crushing the bed can cause deformities. Yeast, fungal, and bacterial infections, and viral warts can also change the shape of a these body parts. If a person is poisoned from arsenic, horizontal ridges and white lines may develop on them, while silver can make them blue. Chemotherapy and antibiotics can affect the them.2 “Onychorrhexis” refers to brittle nails with longitudinal ridges. “Beau’s lines” are horizontal depressions, and these can be caused by heart attack, severe infections, malnutrition, diabetes, and metabolic disturbances.3 Anemia leaves the blood less oxygenated, which can make tissues look pale. Pale nails may occur in liver disease or diabetes. Thickening and yellowing are likely from a fungal infection. Dark lines might indicate melanoma. Painting them protects them from sunlight; however, it is important to remove polish periodically to check for nail health. Psoriasis can present with “pitting of the nail bed”. Pitting looks like small cracks and depressions in the bed.4
If the nails are lifted, thin, or brittle, that may be a sign that there is something wrong with the thyroid, which regulates growth, energy, and metabolism. “Muehrcke’s lines” are “horizontal white lines”. These may show signs of liver abnormalities, kidney disease, or lack of nutrients and protein, and are “caused by a disruption in blood supply”. Raynaud’s Disease, a vascular problem, or a respiratory disease may cause blue nails, due to lack of oxygen. These conditions are more persistent than slow blood circulation from low temperatures.5 Yellowing may be a sign of chronic bronchitis or from lymphedema (swelling). Pitting in them might also be related to the autoimmune disease alopecia areata, which causes hair loss. Clubbing resulting from low oxygen may be caused by lung disease, but it could indicate inflammatory bowel disease, AIDS, liver disease, or cardiovascular disease. Spoon nails (“koilonychias”) might be from anemia, hypothyroidism, or heart disease. This condition looks like “soft nails…scooped out”. If the tips of them have a dark band (“Terry’s nails”), it may be caused by aging, diabetes, congestive heart failure, or liver disease. “Onycholysis” is a condition where they separate from their beds. This can happen from infection, injury, medications, adhesives/hardeners, psoriasis, or thyroid disease.6 Whitening with darker rims might be hepatitis. Rippled or pitted appearance may occur with arthritis. If the fold is puffy and red, the inflammation could be due to a connective tissue disorder or lupus. Biting or picking can indicate a mental condition, such as anxiety or obsessive-compulsive disorder.7