Every disease has its signature symptoms. For example, thyroid disorders (like hyperthyroidism and hypothyroidism) are most often associated with weight loss and weight gain, respectively. However, doctors frequently link up nail changes with thyroid diseases, too.
The presence of onycholysis often occurs with hyperthyroidism [source: Gregoriou, et al]. Also known as Plummer's nail, this condition occurs when a fingernail -- most often the ring finger or little finger -- or a toenail separates itself from the nail bed. This lifting can occur at the tip of the nail or along the sides.
Because dirt and moisture can easily collect under lifted nails, Plummer's nail can easily lead to bacterial and yeast infections. Therefore, it's important to see a doctor as soon as possible if you notice any separation of your nails. Not only will you require tips on preventing infection, you'll also need to seek treatment for the underlying cause of the condition.
Spoon nails, which are nails that are concave and look scooped away from the finger, can be a symptom of hypothyroidism [source: Mayo Clinic].
How do you know if you have or are at risk for cardiovascular problems? High blood pressure? High cholesterol? Well, yes, those are common indicators. But what about the condition of your nails? As it turns out, there are a number of nail changes that can indicate cardiovascular diseases.
Splinter hemorrhages, which are thin red or reddish brown lines under the nails, can be a sign of heart valve infection or vasculitis [source: Medline Plus]. While they may look like splinters, they're actually lines of blood.
Congenital heart abnormalities can lead to clubbing of the nails [source: Medline Plus]. In clubbing, nails soften and appear to float above the nail bed, which has usually become wider and rounder than normal. Additional nail signs that can indicate cardiovascular problems are spoon nails (nails that look scooped away from the finger) and pale or blue-tinged nails [sources: Mayo Clinic; WebMD].
➨Anxiety and Stress
If you're a nail-biter, you're not alone. About 50 percent of kids and teens in the United States ages 10 to 18 bite their nails -- as do about 23 percent of adults ages 18 to 22. It's a hard habit to quit, but by age 30, most people have given it up [source: WebMD].
Nail-biting is a nervous habit, like fidgeting and thumb sucking, and people do it when they're stressed or bored. Mild nail-biting won't cause permanent damage, but it does leave your hands looking unkempt and bloody, and could also leave you susceptible to infection in your fingers and your mouth. To help quit, try stress-management methods and physical barriers such as bitter-tasting nail polish. Or, keep nails looking nice with frequent manicures -- tidy nails may deter you from gnawing.
Sometimes, though, nail-biting and picking is severe enough to be categorized by mental health professionals as an impulse-control disorder. It could indicate an anxiety or compulsive disorder and may require behavior therapy. If nail-biting is accompanied by hair pulling or self-mutilating behaviors, see a doctor.
If you frequently paint your fingernails, you'll notice they tend to have a yellowish hue after you've removed the nail polish. However, if your nails remain yellow over a period of days or after a lightening remedy (such as dipping your nails in lemon juice), the discoloration could have a more serious cause: diabetes.
Diabetes can lead to yellowing of both the skin and nails, but is usually more evident in nails [source: Huntley]. The color change is probably caused by glucose connecting with the collagen proteins in the nail [source: Oz].
If your yellow nails are not going back to a normal shade, and if you're also experiencing other symptoms of diabetes like increased thirst and urination, you should see your doctor right away.
Matching your nail color to your lip color can be a beauty strategy. But when you're sporting a light shade of blue on your nails and lips and cosmetics aren't involved, you could be in immediate danger.
Blue nails (particularly when paired with blue lips) can mean that you have an oxygen-related health problem, such as [source: Weil]:
In addition to pulmonary problems, blue nails can also indicate certain heart conditions [source: WebMD]. If your nails have turned blue, regardless of condition, it's usually a sign that your illness has become severe. Emergency medical attention might be needed.
Generally, arthritis is thought of as an achy-joint disorder that affects the elderly. There is a type of arthritis like that. It's called osteoarthritis, and it is very common. However, there are actually more than 100 diseases that qualify as types of arthritis [source: Arthritis Foundation]. The following conditions in the arthritis family can sometimes lead to nail changes:
Osteoarthritis: Weak nails caused by selenium deficiency are often observed in people with this most widespread form of arthritis [source: Arthritis Foundation].
Psoriasis: Yellow nails, rippled nails (when the surface of the nail has a pitted or rippled look) and splinter hemorrhages all can be signs of psoriatic arthritis [sources: WebMD; Gregoriou, et al].
Lupus: Puffy nail fold, a symptom when the skin around the base of the nail swells, is often seen in connective tissue disorders like lupus [source: WebMD].
Rheumatoid arthritis: Red lunula (the lunula is the crescent shape in the nail bed) in rheumatoid arthritis is often due to prednisone treatments for the disease [source: Gregoriou, et al].
Kawasaki disease: This disorder can lead to onychomadesis, the shedding of nails [source: Gregoriou et. al].
Accidents happen -- who hasn't unintentionally caught a finger in a door or dropped something heavy on toe? Mild trauma to the nail bed can cause small, white spots (leukonychia[/url]) in the nail plate that are harmless -- they grow out as the nail grows and eventually you'll clip off the damaged part of the nail. A more severe injury to the nail bed can cause dark spots or streaks on or under the nail, nail detachment (onycholysis[/url]) and splinter hemorrhages
Nail injuries can also happen during a manicure or pedicure. Nail polish and remover are drying and cause brittleness. And if you're a chronic nail-biter, try to quit the habit -- it can lead to nail deformities, as well as infections.
You are what you eat: Beauty on the inside will reflect beauty on the outside. Healthy nutritional choices include omega-3 fatty acids, lean proteins and iron to help support healthy hair, skin and nails.
Nails can reflect some nutritional deficiencies, such as low levels of iron, biotin and protein -- although protein deficiencies are rare in the United States [source: Mayo Clinic].
Most nail problems aren't associated with your nutrition, but if you have an iron deficiency, your nails may disclose it. Pale, whitish nail beds are a common symptom of anemia. With more severe deficiencies, the fingernail may change shape -- a condition called koilonychia (also known as spoon nails) in which the nails are thin and concave with raised vertical ridges.
You might think skin cancers only appear in areas of the body most obviously exposed to the sun --like the nose or ears, for example. While many skin cancers do commonly occur in such areas, the deadliest kind -- melanoma -- can show up under a nail. Known as acral lentiginous melanoma, the kind of melanoma found under nails is the only skin cancer that is more common in African Americans and Asians than it is in Caucasians in the U.S. [source: Skin Cancer Foundation].
Acral lentiginous melanoma usually appears as dark lines underneath the nail, so if you notice this symptom, see your doctor right away. This type of skin cancer is known to advance quickly.
Another tip: If you get an annual skin cancer check by a dermatologist, be sure to remove any nail polish before showing up for your visit. This will allow the doctor to check your fingernails and toenails for signs of melanoma.
Painful, red and itchy skin around your nails is a pretty big clue that something's not right. Just like other parts of your body, your fingernails and toenails are prone to infection, usually occurring in adults and caused by fungus (such as yeast), bacteria (such as Staphylococcus) and viral warts. Nail infections don't necessarily indicate larger, systemic health problems but they do need to be treated by a doctor, especially if you have a medical condition that weakens your immune system.
Fungus is the most common perpetrator, infecting about 12 percent of Americans [source: American Academy of Dermatology]. It can cause nails to become thick and crumbly and change color, taking on a blue-green hue. Fungus is notoriously difficult to treat, so see a doctor for medicine and expect to see results only after your nails have gone through a complete growth cycle (a few months).
Bacteria and viruses also both cause unsightly changes to nails. Bacterial infections target the skin under and around the nail and can lead to nail loss if not treated. Skin viruses cause warts around and sometimes under the nail, which a doctor can freeze off or chemically treat to remove.
Unkempt artificial nails, unsanitary manicure equipment and vigorous manicuring can all increase the chances of infection. Always be sure to properly -- and gently -- clean your nails, fingernails, toenails and artificial nails, and buy your own manicure tools to reduce the spread of bacteria from person to person.