Healthy nails should be smooth and uniform in color, but abnormalities in shape, color, and texture are common; the majority of people will experience a nail disorder at some point, often due to environmental factors or infection.
In some cases, though, changes in the nail indicate an underlying health condition with wider implications, which means these little pieces of keratin can give us valuable insight into our overall health.
Thick nails can be caused by a number of factors, most commonly aging, trauma, poor circulation, and fungal infection. In some cases, thickened nails may be a symptom of an underlying condition such as psoriasis, eczema, rheumatoid arthritis, or diabetes.
Environmentally speaking, toenails sometimes grow thicker due to pressure from ill-fitting shoes.
Yellow nails are often caused by frequent application of nail polish, which causes the nail to become discolored over time, or by a fungal infection. Diseases that may cause yellow nails are those responsible for thyroid inflammation, as well as liver disease and respiratory diseases like tuberculosis and sinusitis.
Some medications, such as mepacrine (an anti-malarial drug), may also cause yellow discoloration. If yellow nails are present alongside lower leg swelling and respiratory symptoms, it could be a disease called yellow nail syndrome, but this is very rare.
White spot discoloration, also known as leukonychia, is the most common nail abnormality. It occurs when the layers of keratin that make up the nail get separated or damaged, or air gets trapped between them, usually as a result of trauma. Another common cause is a fungal infection.
White bands, on the other hand, may be an indication of a vitamin deficiency, liver or heart disease, diabetes, or a reaction to chemotherapy drugs.
Nail discoloration can occur for many reasons. Green-black nails can be caused by bacteria overgrowth, particularly under loose nails. Brown nails are commonly caused by nail polish discoloration or pregnancy but could also indicate malnutrition or thyroid disease. Half-white, half-brown nails, or Lindsay's nails, are often seen in people with kidney failure, and are sometimes also experienced by those living with AIDS or receiving chemotherapy.
Look out for a dark stripe affecting only one nail, as this could be a sign of skin cancer and should be seen by a doctor.
Brittle nails are a common complaint and are usually caused by age or everyday wear and tear, including repeated exposure to water or chemicals like nail polish. In some cases, brittle nails can be caused by a fungal infection, a condition called lichen planus, anemia, Raynaud’s syndrome, psoriasis, or a thyroid issue. In rare cases, brittle nails may indicate a nutritional deficiency.
The most common reason for a nail to turn white is that the nail, or part of it, has become separated from the nail bed due to injury. Other common causes of white nails include fungal infection or a condition called Terry’s nails, which is the result of decreased blood flow to the nail bed.
Terry’s nails is characterized by white nails with dark tips, and some people develop this as they age. Other causes include liver cirrhosis, kidney disease, diabetes, anemia, or thyroid problems.
An uneven nail surface with pits or dents is usually caused by psoriasis. Research suggests that up to 50% of people with psoriasis will also experience a nail disorder. Other causes include psoriatic arthritis, eczema, lichen planus, and reactive arthritis.
Alopecia areata can also cause nail pitting, though the dents are usually fine, not rough. In very rare cases, the inflammatory condition sarcoidosis can cause nail pitting.
The parts where the side of the nail meets the skin are called the lateral nail folds. Often this skin becomes dry, irritated, and sometimes painful. Although unpleasant, this is rarely cause for concern. Common causes include nail biting, cold weather, repeated exposure to water or chemicals, and infection.
Psoriasis, eczema, and dermatitis can also irritate the skin around the edge of the nails.
Small red or brown streaks under the nails are usually damaged blood vessels, most likely resulting from trauma to the nail. If more than one nail is affected without an obvious cause, such as an injury, it could be a sign of lupus, endocarditis, or psoriasis.
Dark stripes affecting all the nails are common in people of color and aren’t usually a cause for concern. A dark stripe under just one nail, especially one that grows larger or affects the surrounding skin, could be a sign of skin cancer and should be assessed by a doctor.
Concave nails, also known as spoon nails or koilonychia, are usually caused by iron deficiency anemia. Sometimes, concave nails are a sign of a fungal infection, psoriasis, or lichen planus. They may also be hereditary, caused by an injury, or by environmental factors such as tight shoes or overexposure to petroleum products.
Thumb sucking in babies and toddlers can also be a cause. Other diseases that can cause concave nails include diabetes, heart disease, hypothyroidism, and lupus.
Fingernails developing a blue tinge is a normal response to cold weather. Blood vessels constrict in cold conditions so that the supply focuses on vital organs, so there’s not always enough blood reaching the nails. So long as normal color returns to the nail when it’s warmer, there’s no cause for concern.
If the blue tinge persists, it may be a sign of something else causing restricted blood flow. Conditions that restrict blood flow include Raynaud’s syndrome, carbon monoxide poisoning, heart disease, and respiratory diseases like emphysema or asthma.
Vertical nail ridges are common and generally become more apparent with age. Horizontal ridges, called Beau’s lines, happen when something interrupts nail growth, such as trauma or injury, damage caused by acrylic or gel nails, severe illness with fever, or a reaction to chemotherapy.
In some cases, a zinc deficiency can cause horizontal nail ridges. Often, the ridges are not noticeable until long after the initial cause has disappeared. This is because fingernails take four to six months to grow out fully, and toenails take six to 12 months.
Nail biting is a habit that affects 20 to 30% of Americans. Often it's a self-soothing habit that's more prevalent during times of high stress or anxiety. Most people grow out of it or are able to stop by using deterrents such as foul-flavored nail polish.
If a person can’t stop biting their nails, they may have a condition called onychophagia, which is considered a body-focused repetitive behavior (BFRB). People with other types of compulsive behavior are more likely to have onychophagia, as are people with ADHD, Tourette’s, or separation anxiety.
A puffy or inflamed nail bed, also known as paronychia, results from trauma, irritation, or infection. It happens when bacteria enter broken skin at the point where the nail and skin meet. Risk factors include trauma, nail-biting, ingrown nails, working with water, and repeat exposure to irritants.
Some cases of paronychia can be treated at home, but serious or recurring cases will need medical attention.
Clubbed nails are caused by increased blood flow to the fingertips, which results in the tissue beneath the nails becoming rounded. The nail then grows over the rounded tip. Often, it runs in families and is harmless. If it develops suddenly, it could be a symptom of inflammatory bowel disease, lung or heart disease, liver cirrhosis, or cancer.
The nail can separate from the nail bed for a number of reasons, the most common of which is physical trauma. This could be an acute injury or prolonged wear and tear, such as tapping, wearing tight shoes, or getting too many manicures. Fungal infection, psoriasis, and a reaction to chemical exposure are also common causes.
Separation usually doesn’t affect every nail. If it does, it may be a sign of hyperthyroidism or iron deficiency.
This site offers information designed for educational purposes only. You should not rely on any information on this site as a substitute for professional medical advice, diagnosis, treatment, or as a substitute for, professional counseling care, advice, diagnosis, or treatment. If you have any concerns or questions about your health, you should always consult with a physician or other healthcare professional.