What Your Nails Might Be Telling You: 8 Changes Worth a Closer Look
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Your nails can quietly reflect what is going on with your health. Most changes are harmless and cosmetic, but a few are worth a closer look. Here is a calm, plain-English guide, and when it is worth seeing a professional.
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If you take one thing from this article: a new or changing dark streak running down a single nail should be seen by a GP or dermatologist promptly. Most dark marks are harmless (often a bruise), but this is the one worth checking early, just to be sure.
In this guide
CC0 · Wikimedia
Green nailChloronychia (green nail syndrome, Pseudomonas nail infection)
What it looks like
Green nail is a green discolouration of the nail, usually caused by a common environmental bacterium (Pseudomonas aeruginosa) growing under a lifted or damaged nail. The colour can range from greenish-yellow to greenish-brown or greenish-black, and the nail edge is often lifted from the nail bed with mild swelling of the surrounding skin fold.
Common causes
The bacteria thrive in moisture and grow where a nail is already lifted or weakened. Common contributors include frequent or prolonged contact with water, soap or detergents (for example dishwashing, cleaning, or healthcare work); a nail already separated from its bed (onycholysis); ongoing inflammation of the skin around the nail (paronychia); nail trauma; and underlying issues such as psoriasis, a fungal nail, or artificial/gel nails that trap moisture.
When to see a professional
This is general information, not medical advice. See a GP, dermatologist or podiatrist if the green colour does not settle once the nail is kept dry, if it spreads, or if there is pain, increasing redness, swelling or discharge, or if you have diabetes or a weakened immune system. Importantly, because dark green-black changes under a nail can occasionally look similar to other conditions, any NEW or CHANGING dark streak or dark patch in a nail should be checked by a doctor PROMPTLY to be sure of the cause. A clinician can confirm what it is, sometimes with a swab or culture, and advise on care.
Public domain · Wikimedia
Red, swollen, tender nail foldParonychia
What it looks like
Paronychia is inflammation of the skin fold around a fingernail or toenail, where it usually looks red, swollen and tender, sometimes with a build-up of pus near the cuticle. An acute case tends to come on quickly in one nail, while a chronic case develops slowly and may affect several nails over weeks or longer.
Common causes
Often follows minor damage to the cuticle or nail fold, such as nail biting, picking, aggressive manicures, hangnails, artificial nails or an ingrown nail. Acute cases are commonly linked to bacterial infection (and sometimes the cold-sore virus or Candida yeast). Chronic cases are associated with frequently wet hands, skin irritation or dermatitis, and are more common in people with diabetes or a weakened immune system.
When to see a professional
Consider seeing a GP if the area is very painful, the redness or swelling is spreading, pus is collecting, it is not settling, or you have diabetes or a weakened immune system. Seek prompt medical care for fever, red streaks spreading up the finger, or a clear pus pocket. Separately, and importantly, see a doctor or dermatologist promptly about any new or changing dark streak or dark pigment in or under a nail, as this needs assessment to rule out melanoma. This is general educational information, not medical advice or a diagnosis.
CC BY-SA 4.0 · Wikimedia
Yellow, thick or crumbly nailOnychomycosis (fungal nail infection)
What it looks like
Onychomycosis is a common fungal infection of the nail, most often a toenail. It tends to make the nail look discoloured (yellow, white, grey or sometimes green), thickened, brittle and crumbly, often starting at the edge or tip and spreading inward.
Common causes
It is usually caused by dermatophyte fungi (most commonly Trichophyton rubrum), and sometimes yeasts or moulds. Things that make it more likely include warm, damp feet, sweaty shoes or trainers worn for long periods, untreated athlete's foot, nail injury, using communal showers or pools, older age, diabetes, and a weakened immune system.
When to see a professional
A pharmacist can advise on over-the-counter antifungal treatments if the nail is bothersome. See a GP if pharmacy treatment has not worked, several nails are affected, the nail is painful, or you have diabetes or a weakened immune system, since nail problems can be more serious in these cases. A GP or dermatologist can confirm what is going on, as other conditions can mimic a fungal nail. Importantly, see a doctor PROMPTLY for any NEW or CHANGING dark brown or black streak or band under a nail, especially if it is widening, has uneven colour, or the pigment spreads onto the surrounding skin, as this needs to be checked to rule out a melanoma (a serious skin cancer). This is general educational information, not a diagnosis or medical advice.
CC BY 4.0 · Wikimedia
⚠ See a doctor promptly
A new or changing dark streak down the nailSubungual melanoma (melanoma of the nail unit)
What it looks like
Subungual melanoma is a rare but serious form of skin cancer that develops from pigment-producing cells (melanocytes) in the nail matrix. It typically appears as a brown or black band running lengthwise down a single nail, which may widen over time, become irregular in colour, or spread onto the surrounding skin.
Common causes
Most dark nail streaks are not cancer. Common harmless causes include a bruise under the nail (from knocks or injury), fungal infection, a benign mole or freckle in the nail, certain medicines, and natural pigmentation that often appears across several nails in people with darker skin. Unlike most skin cancers, nail melanoma is not linked to sun exposure; past injury or trauma to the nail may play a role.
When to see a professional
See a GP or dermatologist promptly if you notice a NEW dark streak in a single nail, or an existing streak that is changing, widening (especially wider than about 3 mm), becoming irregular or darker, spreading onto the skin around the nail, or affecting the thumb or big toe. This is general educational information, not a diagnosis. Only a doctor can tell a harmless streak from a serious one, and they may take a small sample (biopsy) to be sure. Because nail melanoma can be missed or diagnosed late, do not simply wait and watch a streak you are unsure about: get it checked.
CC BY-SA 3.0 · Wikimedia
Nail lifting (nail separating from the bed)Onycholysis
What it looks like
Onycholysis is when the nail plate gradually separates from the skin underneath it (the nail bed), most often starting at the free edge and lifting back toward the cuticle. The lifted area usually looks whitish or opaque because there is now air beneath it, with a sharply defined, often irregular border against the healthy pink part of the nail.
Common causes
It often follows everyday causes such as trauma or repetitive injury, aggressive manicures, and prolonged water or chemical exposure. It can also be linked to skin conditions like psoriasis or lichen planus, fungal or yeast (Candida) nail infections, certain medications (including some that cause sun sensitivity), and sometimes thyroid problems or other systemic factors. In some cases no cause is found.
When to see a professional
Because lifted nails can trap moisture and lead to a secondary fungal or bacterial infection (sometimes showing as green, yellow or dark discolouration), it is worth seeing a GP or dermatologist if the lifting spreads, becomes painful or discoloured, or does not improve. Importantly, see a doctor PROMPTLY if you notice a new or changing dark brown-to-black streak or band in the nail, a widening band, pigment spreading onto the surrounding skin, or unexplained lifting of a single nail, as these need professional assessment to rule out serious causes including melanoma. This is general educational information, not a diagnosis or treatment advice.
CC BY-SA 4.0 · Wikimedia
White spots or marksLeukonychia
What it looks like
Leukonychia is white discolouration of the nail, ranging from tiny dots or specks to lines, bands, or whitening across the whole nail. It is a common type of nail discolouration and is usually harmless.
Common causes
Minor injury to the nail or to the area where it grows is the most common cause, for example knocks and bumps, nail biting, or vigorous manicuring. Less often, white nails can relate to a fungal nail infection, allergic reactions to nail products, or certain medicines. When whitening is widespread or covers whole nails, it can sometimes be linked to general health conditions affecting the liver, kidneys or heart.
When to see a professional
Most isolated white spots are harmless and simply grow out over time, so they usually need no treatment. See a GP or dermatologist if white marks are widespread, cover whole nails, keep coming back, or appear alongside other symptoms, so any underlying cause can be checked. White spots are not the same as a dark brown or black streak running along the nail. See a doctor promptly about any new, changing, widening, uneven, or darkening dark streak, or one that spreads to the surrounding skin or cuticle, as this needs proper assessment.
Pale nail bedsNail bed pallor (sometimes described as apparent leukonychia)
What it looks like
Healthy nail beds usually have a soft pink undertone because of the blood vessels beneath the nail. When the nail beds look unusually pale, washed-out or whitish rather than pink, this is called pallor. It is a general sign, not a diagnosis, and tends to affect all the nails fairly evenly rather than just one.
Common causes
Often simply cold hands or briefly pressing on the nail, which reduces blood flow. More evenly pale nail beds can sometimes reflect anaemia (a low level of healthy red blood cells), commonly from iron deficiency. Some people naturally have paler nail beds. Pallor seen across the nails, skin and inner eyelids together is more suggestive of anaemia than pale nails alone.
When to see a professional
See your GP if your nail beds (and skin) look persistently pale, especially alongside tiredness, breathlessness, headaches or noticeable heartbeats, as a simple full blood count test can check for anaemia. Seek urgent medical care for severe breathlessness, chest pain or feeling faint. Separately, and importantly, see a doctor promptly about any NEW or CHANGING dark brown or black streak or band running down a single nail, so it can be assessed and melanoma ruled out. A GP or dermatologist can advise; this is general information, not medical advice or a diagnosis.
CC BY-SA 4.0 · Wikimedia
Brittle, splitting or peeling nailsOnychoschizia (splitting/peeling) and onychorrhexis (lengthwise ridging and splitting)
What it looks like
A common, usually harmless change where the nail becomes weak and the free edge splits, flakes or peels into thin layers (onychoschizia), often with fine lengthwise ridges or splits running up the nail (onychorrhexis). It tends to affect several nails and is more noticeable with age.
Common causes
Most often repeated wetting and drying of the hands, plus harsh soaps and detergents. Other contributors include nail cosmetics and solvents (polish removers, hardeners, gel and acrylic manicures), occupational chemical exposure, minor trauma, and natural ageing. Less commonly it can be linked to skin conditions such as psoriasis or lichen planus, fungal nail infection, some medicines, or general health and nutritional factors.
When to see a professional
This is general educational information, not medical advice. See a GP or dermatologist if the problem persists despite gentle nail care, if only one nail is affected or there is pain, bleeding, swelling, pus, or marked colour or shape change, or if you have a health condition or medicine you think may be involved. See a doctor PROMPTLY if you notice a new, widening or changing dark brown or black streak or band in or under a nail, as this should be checked to rule out melanoma. A clinician can tell harmless changes from those needing tests; this content makes no diagnosis and offers no cure claims.
Looking after your nails, day to day
Healthy nails like the boring stuff: keep hands dry where you can, wear gloves for cleaning and dishwashing, do not pick or over-buff, look after your cuticles gently rather than cutting them aggressively, and give polish or gels an occasional breather. A good hand cream and a little cuticle oil go a long way.
Want a gentle, healthy-nail manicure? Our team at Verdo Nails & More is careful with cuticles and prep, or browse hand and nail care at verdocosmetics.com.
When in doubt, ask
Nails grow slowly, so changes take time to show and time to grow out. If something is not settling, is spreading, or you are simply unsure, a GP, dermatologist or podiatrist can tell you what is going on, often with a quick look. There is never any harm in peace of mind.
Image credits
Clinical photographs are real, used under their respective free licences, and remain the property of their authors.
- Green nail: Chloronychia.2.jpg, Ekem (CC0), via Wikimedia Commons.
- Red, swollen, tender nail fold: Paronychia.jpg, Chris Craig (Ciotog) (Public domain), via Wikimedia Commons.
- Yellow, thick or crumbly nail: 1501 Tinea Unguium.jpg, Dr.Gandikota Raghurama Rao (CC BY-SA 4.0), via Wikimedia Commons.
- A new or changing dark streak down the nail: Longitudinal melanonychia.png, Seungjun Lee & Seokchan Eun (CC BY 4.0), via Wikimedia Commons.
- Nail lifting (nail separating from the bed): Detachment of a fingernail.jpg, Threecharlie (CC BY-SA 3.0), via Wikimedia Commons.
- Brittle, splitting or peeling nails: Beau's lines in an adult.jpg, Cagaso21 (CC BY-SA 4.0), via Wikimedia Commons.
- White spots or marks: Idiopathic Leukonychia totalis.jpg, Alborz Fallah (CC BY-SA 4.0), via Wikimedia Commons.
Sources
- https://dermnetnz.org/topics/pseudomonas-skin-infections
- https://pmc.ncbi.nlm.nih.gov/articles/PMC4298286/
- https://dermnetnz.org/topics/paronychia
- https://www.aad.org/public/everyday-care/nail-care-secrets/basics/nail-changes-dermatologist-should-examine
- https://dermnetnz.org/topics/fungal-nail-infections
- https://www.nhs.uk/conditions/fungal-nail-infection/
- https://dermnetnz.org/topics/melanoma-of-the-nail-unit
- https://my.clevelandclinic.org/health/diseases/subungual-melanoma
- https://dermnetnz.org/cme/principles/examination-of-the-nails
- https://dermnetnz.org/topics/white-nail
- https://dermnetnz.org/topics/nail-terminology
- https://www.nhs.uk/conditions/iron-deficiency-anaemia/
- https://dermnetnz.org/topics/onycholysis
- https://my.clevelandclinic.org/health/diseases/melanonychia
This article is general educational information only. It is not medical advice, a diagnosis, or a treatment recommendation, and it has not been evaluated by Medsafe. Verdo is not a medical provider. Always see a qualified healthcare professional about any nail or skin concern, especially a new or changing dark streak in a nail.