Nails can reveal much more about a person's health than you may have thought. Certain conditions can cause changes in the color, shape, or texture of nails. Some of these changes might be a sign of a serious health condition.

Koilonychia is a condition that affects the shape of nails. The nails of people with koilonychia curve inward and look like a spoon.

In many cases, koilonychia is a symptom of another condition.

While there are many different causes of koilonychia, sometimes the cause is unknown. Read on for more information regarding some of the conditions associated with koilonychia:

Nutrition deficiency

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Changes to the nails may signify a serious health condition.

Iron deficiency is the most frequent cause of koilonychia. Iron deficiency anemia is the world's most common nutritional deficiency disease and is most prevalent among women of childbearing age and children.

Iron deficiency can arise from one of the following health problems:

Inadequate intake of folate, protein and vitamin C can also contribute to iron deficiency.

People with Plummer-Vinson syndrome, a condition that can occur in those who have a long-term iron deficiency, may also cause koilonychia.

Autoimmune conditions

People with lupus erythematosus sometimes have koilonychia, but they typically have other characteristic symptoms as well. Other symptoms include tiredness, fever, and swollen joints.

Certain inflammatory skin conditions, including psoriasis and lichen planus, are associated with koilonychia. Both of these skin conditions take the form of rashes involving the immune system.

Environmental exposures

Koilonychia has been linked to products that contain petroleum. Some people, such as hairstylists, may frequently work with petroleum-containing products, which could put them at higher risk for koilonychia.

People that live at high elevations may also have a greater risk for koilonychia. The air at higher altitudes contains less oxygen than it does at lower levels, and reduced oxygen leads the body to produce extra red blood cells, which depletes the body's supply of iron.

In 2003, researchers carried out a study among people living at high altitude in the Ladakh region of India. The study showed that almost half of the participants had koilonychia, and it was more common in middle-aged people.

Interestingly, the traditional diet of those living in this region is low in iron, which also puts them at risk for koilonychia.


Koilonychia can occur as a result of some genetic conditions, such as hemochromatosis and nail-patella syndrome.

Other conditions

Koilonychia has links with the following conditions:

Risk factors

People who are older or have poor blood flow to their fingers and toes may have thinner nails, which may increase their risk of developing koilonychia.

People who have a higher risk of iron deficiency, such as menstruating women and vegetarians, may be at greater risk for developing koilonychia.

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A doctor should be consulted if any nail abnormalities are present.

Flat nails can be one of the first signs of koilonychia, occurring before the characteristic concave shape develops.

The nails of people with koilonychia are also sometimes described as being able to hold a drop of water.

Typically, koilonychia is easier to notice on fingernails than toenails.

Koilonychia can have different meanings based on the age of the person with the condition.

In adults, koilonychia may be a sign of a serious health condition.

Koilonychia occurs commonly in infants, especially on their big toes, since their nails are fragile. It usually goes away on its own but may take a couple of years. However, koilonychia could also be related to a disorder that a baby is born with.

A small, observational study in newborns found that slightly more than 30 percent of the infants had koilonychia.

When to see a doctor

Nail abnormalities may provide important information about a person's health, so anyone with nail abnormalities should see their doctor.

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A lack of iron in the diet may cause koilonychia.

Treatment for koilonychia will depend on the cause of the condition. To determine the cause, doctors will likely take a full medical history, perform a physical exam, and may order blood tests.

Depending on the cause of iron deficiency, koilonychia may improve by eating foods that contain good sources of iron or by taking iron supplements.

Meat and animal products are considered the best sources of dietary iron. For vegetarians, good sources of iron include beans, leafy greens, and fortified grain products.

The recommended iron intake for vegetarians is 1.8 times higher than for meat-eaters to make up for the lower absorption level from plant-based foods. In many countries, wheat products and infant formulas have iron added to them.

Combining vegetarian sources of iron with vitamin C rich foods, such as citrus fruits, can also help increase iron absorption.

Some causes of koilonychia, such as genetic conditions, cannot be prevented, however.

Recommended iron intake

The recommended daily allowance (RDA) for iron depends on age and gender:

1-3 years7 milligrams (mg)
4-8 years10 mg
9-13 years8 mg
14-18 years11 mg
19 years and older8 mg
9-13 years8 mg
14-18 years15 mg
19-50 years18 mg
51 years and older8 mg
During pregnancy27 mg

It can take time for nails to recover their usual shape after the cause of koilonychia has been treated.

According to a report in the Cleveland Clinic Journal of Medicine, fingernails take approximately 6 months to regrow fully, while toenails take 12-18 months.