What Your Nails Can Tell You About Your Health

During medical school, nails were among the topics in my anatomy course that I found most challenging. At first, I struggled to tolerate the sight of painful injuries involving nails.

That discomfort may have begun when I watched somebody briskly pull a plaster from a stubbed big toe – and remove the entire toenail with it. Ouch. I have got over it since, fortunately, because a patient’s nails can reveal a great deal to doctors about their health.

Like hair, fingernails and toenails are extensions of the skin. Made from keratin, a resilient substance, they grow towards the tip of each finger or toe to create a hard plate. The cuticle – the band of skin that covers where the nail meets the skin – provides further defence against injury and infection.

Pay attention to alterations in your nails’ texture or appearance, as these may offer valuable indications of your health. These are some important signs to watch for.

Spoon-shaped nails

Healthy fingernails and toenails usually have a gently convex curve, with no hollows or indentations. Koilonychia, by comparison, causes nails to become concave. Sometimes, the central hollow is deep enough to retain a drop of liquid, much like medicine sitting in a spoon, which is why it is commonly called "spoon nails". Nails affected by this condition generally appear thinner and may also become more fragile.

Koilonychia may be a sign of anaemia, where too few red blood cells are circulating to deliver oxygen to the body’s tissues. This is linked with iron deficiency. Poor diet, coeliac disease and cancer of the gastrointestinal tract are among the possible causes of low iron.

Because they work with petroleum-based solvents present in engine oils and perming agents, mechanics and hairdressers may face a particular risk of koilonychia. But spoon-shaped nails have a wide range of potential causes, so consult your doctor if the condition persists for a long time.

Discoloured nails

Under normal circumstances, the nail beds – the skin below the nails – should be a well-perfused pink. Illness or infection may discolour either the nail bed or the whole nail. For example, yellow nails can suggest a fungal infection or changes caused by a skin condition, including psoriasis.

Leukonychia is the medical name for white nail discolouration, and it can present in several ways.

Sometimes, white nail markings may point to poisoning with heavy metals such as lead or arsenic. Both remain issues in many countries around the world owing to pollution of water supplies.

When whiteness covers an entire nail and affects several nails, a lack of protein in the circulation is a more likely explanation. This might indicate liver disease or kidney disease.

Small white marks, however, are most likely to be caused by some type of trauma. This can range from stubbing a toe or dropping a heavy object on it to shutting a finger in a door. Nail biting and excessively vigorous manicures, both common habits, can also damage the nail.

If you have ever trapped a finger or stubbed a toe, you may also have seen the nail turn dark purple, blue or red afterwards. This is known as a subungual haematoma: blood collecting between the nail and the nail bed after an injury. Although these usually resolve on their own with time, they can lead to infection or cause the nail to separate from its bed.

Emergency nail tests

In a medical emergency, doctors often inspect a patient’s nails to assess blood oxygen saturation. They use a pulse oximeter, which clips onto a finger, shines light through the fingertip and measures the volume of blood passing through it. This shows how much oxygen is entering the blood and, consequently, how well the heart and lungs are functioning.

Clinicians can also assess the effectiveness of circulation with the capillary refill time (CRT) test. They press a nail or fingertip for five seconds, causing the skin beneath it to blanch.

Once the pressure is released, the skin should regain its original colour within two seconds. If it takes longer, you may be cold or dehydrated, or have poor peripheral perfusion. This means that either the heart is not pumping strongly enough or something is limiting blood flow to the most distant areas of the body, potentially because of shock.

Pressing on nails is also used when assessing a patient who is unconscious or drowsy. The test is included in the Glasgow Coma Scale, which evaluates responsiveness and the degree of impaired consciousness in patients.

What to do if you notice something unusual

These are far from the only nail problems. Other examples include nails that crumble, have pits or ridges, are clubbed or swollen, or have red lines beneath them. The possible diagnoses are equally broad, ranging from minor conditions to serious ones.

If you are concerned by a change in the shape of your nails or by nail discolouration, have them examined by your GP. The same applies to severe nail injuries, particularly if the nail comes off. Should you damage the skin beneath a nail, look after it correctly to avoid complications such as infection, and check for other injuries, including a broken bone.

One final caution: artificial or painted nails can conceal visible changes. Take care not to cover up your nails, and pay attention to what they could be saying about your health.

Dan Baumgardt, Senior Lecturer, School of Physiology, Pharmacology and Neuroscience, University of Bristol

This article is republished from The Conversation under a Creative Commons licence. Read the original article.