A nail that suddenly looks different—with a white spot, dark streak, ridge or lifted edge—is most often due to minor damage or the nail’s normal growth cycle, not an illness. Still, there are several patterns worth paying attention to: a dark streak that does not move or spreads onto the skin around the nail, red and swollen skin, or a nail that lifts from the nail bed and changes color when you cannot remember injuring it. The following guide groups the most common changes according to what you can actually see on the nail—color, texture, shape and the condition of the surrounding skin—and explains for each when it is normal and when it is wiser to have it checked.
- White spots on nails usually appear after a minor knock and grow out on their own over a few months.
- A dark streak under a nail, especially if it spreads onto the surrounding skin, needs to be checked by a doctor, because a change in pigmentation cannot be reliably assessed with the naked eye.
- Red, swollen or painful skin around a nail, and a nail that is lifting or crumbling, are reasons to see a doctor, not to cover it with polish.
- Until someone has checked the change, do not apply polish, gel or press-on nails to the affected nail.
Colors that are usually no cause for concern
Of all color changes, the most common is the one that looks the most noticeable at first glance, yet is usually the least serious.
White spots (leukonychia)
Small white spots or streaks on the nail plate are common and usually harmless, according to Cleveland Clinic—they are most often caused by a minor knock to the nail, nail biting or tight shoes, not an illness (source: White Spots on Nails (Leukonychia) — Cleveland Clinic). Because the spot forms where the nail was growing at the time of the damage, it gradually moves out with the nail and disappears—usually over months, not days.
Even so, it is worth having the spots checked if other new nail symptoms appear alongside them—crumbling, a change in color or ridges—or if you have general symptoms such as weakness, fatigue, blurred vision, confusion or shortness of breath, or if the spots do not disappear after treatment.
Colors that make it sensible to see a doctor
With other color changes, a doctor’s appointment is more often appropriate because they can be related to processes you cannot identify just by looking.
A dark streak under the nail
Doctors assess a dark streak running lengthwise under the nail (melanonychia) using the so-called ABCDEF rule: it takes into account the patient’s age, the width of the streak, changes in its color over time, which finger or toe is affected, pigment spreading onto the surrounding skin, and a family history of skin cancer. Pigment that extends past the edge of the nail onto the surrounding skin—the so-called Hutchinson sign—is an important, though not conclusive, indication in the medical literature that the streak needs to be assessed by a doctor sooner (source: Melanonychia — PubMed Central). The point is not for you to diagnose the streak yourself, but to understand why a doctor pays extra attention to it and not to keep a new or changing streak to yourself.
Yellow, green or dark discoloration
A nail discoloration that differs from its usual color—whether yellowish, greenish or darker—and appears together with thickening or crumbling of the nail is more likely to be a sign of a fungal nail infection than a cosmetic issue, according to Guy's and St Thomas' NHS Foundation Trust: discoloration, thickening and crumbling are among the typical signs caused by this infection (source: Fungal nail infections — Guy's and St Thomas' NHS Foundation Trust).
Texture: ridges and dents
The surface of a nail sometimes reveals more than its color, especially when pronounced ridges or tiny dents appear.
Deep ridges (Beau’s lines)
Deep horizontal ridges across the nail, known as Beau’s lines, mark the place where nail growth temporarily stopped because of an illness, fever or injury, according to the American Academy of Dermatology (source: 12 nail changes a dermatologist should examine — AAD). As the nail grows longer, the ridge gradually grows out on its own.
Tiny dents
Small, pinprick-like dents (pitting) are more often associated with skin conditions such as psoriasis, atopic eczema or alopecia areata than with ordinary nail wear, according to the same source.
Nail shape: curving and spoon-shaped nails
Changes in shape develop slowly, over months or years, so people often notice them only after some time has passed. Gradual curving of the nail around an enlarged fingertip (so-called clubbing) develops over a long period and is associated with lung, heart, liver or digestive problems, according to the AAD—it is not a diagnosis you can make yourself, but a finding worth mentioning to a doctor (source: 12 nail changes a dermatologist should examine — AAD). A thin, sunken nail that curves inward (a spoon-shaped nail, or koilonychia) is described in general health information as more often linked to iron deficiency than to nail care; if it is accompanied by fatigue or paleness, it is worth discussing with a doctor.
The skin and structure around the nail
The condition of a nail is closely connected to the skin around it and to how firmly the nail is attached to the nail bed.
Red, swollen skin around the nail
Skin along the edge of the nail that becomes red, swollen, warm to the touch or painful (paronychia) is a common reason to see a primary care doctor, according to the NHS, especially if it gets worse or pus appears (source: Nail problems — NHS).
A thickened, crumbling or peeling nail
A nail that thickens, softens, crumbles or lifts away from the nail bed is more likely to be a sign of a fungal infection than a cosmetic problem, according to the same source from Guy's and St Thomas'; at first, it usually does not hurt, which makes it easy to overlook.
When not to leave a nail waiting
The following table brings together the changes from the previous sections so you do not have to look them up again in the text. Split and brittle nails are so common that they deserve their own detailed article—if that sounds like you, you can find the causes and care in a separate article about splitting nails and their causes.
| What you see | Usually | When to see a doctor |
|---|---|---|
| White spots on the nail | minor nail injury; grows out | more appear without an injury, or they do not disappear |
| A dark streak under the nail | uncommon; needs assessment | it is new, changing, or extends onto the surrounding skin |
| Yellow, green or dark discoloration with thickening | fungal infection | it gets worse, hurts or does not go away |
| Deep ridges (Beau’s lines) | after an illness or injury; grows out | it recurs without an obvious cause |
| Tiny dents | often associated with skin conditions | they increase along with skin problems |
| Curving of the nail (clubbing) | develops over months or years | always worth mentioning to a doctor |
| Spoon-shaped nail | often associated with iron deficiency | along with fatigue or paleness |
| Red, swollen skin around the nail | mild irritation | it gets worse, hurts or there is pus |
| A thickened, crumbling or peeling nail | fungal infection | it hurts or does not respond to ordinary care |
What to do before you have it checked
If a nail hurts, is swollen, noticeably discolored or lifting from the nail bed, have it assessed first and only then apply polish, gel or press-on nails: covering it does not address the cause of the change and also makes it impossible to notice if the condition is getting worse. Keep the nail short, clean and fully visible—this makes it easy to tell whether things are improving or not.
If your nails are healthy
For nails that have been checked and are healthy, the Nude press-on nail set is one way to try a different look without polish or gel—and it can also be removed cleanly afterward if you want a change. You can find more about the individual topics in this section, from ridges to discoloration, in other articles on the nail care blog.