An infected toenail typically shows one or more clear signs: discoloration (yellow, white, or greenish), thickening of the nail, pain and swelling around the nail edges, or pus building up near the skin. The type of symptoms you’re seeing points to whether you’re dealing with a fungal infection, a bacterial infection, or something else entirely.
Fungal Infection: The Slow, Painless Change
Fungal toenail infections are by far the most common type, and they’re sneaky because they usually don’t hurt at first. The earliest sign is often a small patch of white or yellow discoloration near the tip of the nail. Over weeks to months, this spreads. The nail gradually thickens, becomes brittle or crumbly at the edges, and may start to separate from the nail bed underneath. You might notice chalky debris collecting under the nail, which gives it that characteristic yellowish, opaque look.
One form shows up as a white, chalky scale spreading slowly across the surface of the nail rather than underneath it. Another starts at the tip and works its way back toward the cuticle. In either case, the infection tends to worsen so gradually that many people don’t realize something is wrong until the nail looks noticeably different from their other toenails.
Fungal infections rarely cause pain unless the nail becomes very thick and presses against the inside of your shoe, or the infection reaches a more advanced stage. There’s typically no redness, warmth, or swelling of the surrounding skin. If you’re seeing color and texture changes in the nail itself without much pain or skin involvement, a fungal infection is the most likely explanation.
Bacterial Infection: Fast, Painful, and Obvious
Bacterial toenail infections look and feel very different from fungal ones. They usually develop around the nail rather than within it, most often along the edges where the skin meets the nail (a condition called paronychia). The hallmark signs are hard to miss: the skin next to the nail becomes red, swollen, warm to the touch, and tender. It hurts when you press on it, and sometimes it hurts constantly.
As the infection progresses, pus builds up under the skin. You may see a white or yellow pocket forming near the nail edge. This can happen quickly, sometimes within a day or two, especially after an ingrown toenail breaks the skin or after you’ve torn a hangnail. Unlike fungal infections that creep along over months, bacterial infections announce themselves within days.
How to Tell It’s Not Just a Bruise
A dark spot under your toenail after stubbing your toe or wearing tight shoes is usually just a bruise (a collection of blood under the nail). Here’s how to tell the difference: a bruise will have a clear edge and will slowly move forward as your nail grows out. For toenails, this can take up to nine months, but you should see the dark area gradually shifting toward the tip over time. Eventually it disappears completely.
If a dark spot doesn’t grow out with the nail, doesn’t have a clear border, or seems to be getting larger rather than migrating forward, that’s a different situation. Melanoma can occasionally develop under a toenail and mimic the appearance of a bruise. A discoloration that stays put while the nail grows deserves a closer look from a doctor.
Signs the Infection Is Getting Worse
Most toenail infections stay localized, but some spread to the surrounding skin. Watch for redness that extends beyond the immediate area around the nail, especially if it’s tracking up your toe or foot. Increasing pain, red streaks moving away from the toe, fever, or a feeling of general illness can signal that bacteria have moved into deeper tissue. This type of spreading skin infection needs prompt treatment.
If you have diabetes, even a mild toenail infection warrants extra attention. Reduced blood flow and nerve damage in the feet (which can dull your ability to feel pain or temperature changes) mean infections can progress further before you notice them. The CDC specifically lists thick yellow toenails, fungal infections between the toes, and ingrown or infected nails as reasons for people with diabetes to see a doctor rather than manage things at home.
What Happens at the Doctor’s Office
For a suspected fungal infection, your doctor may clip a small piece of the nail or scrape debris from underneath it. This sample gets examined under a microscope or sent to a lab to confirm whether fungus is actually present. This step matters because several other conditions, including psoriasis and simple nail trauma, can mimic the appearance of a fungal infection. Lab confirmation avoids months of unnecessary treatment.
For bacterial infections with visible pus or an abscess, the visit is more straightforward. The doctor can usually diagnose it on sight and may need to drain the infected area if pus has collected.
What Treatment Looks Like
Bacterial infections around the nail often resolve within a week or two with proper care, whether that involves warm soaks, drainage, or a course of antibiotics for more serious cases.
Fungal infections are a longer commitment. Oral antifungal medication is typically taken daily for 6 to 12 weeks, but you won’t see the full result until the healthy nail grows in completely, which takes four months or longer. Topical treatments applied directly to the nail can take even longer. One common medicated nail polish requires daily application for close to a year. The key thing to understand is that even effective treatment doesn’t make the existing damaged nail look better. You’re waiting for a new, healthy nail to slowly replace the infected one from the base forward.
Mild fungal infections that aren’t causing pain or spreading don’t always require treatment. Some people choose to leave them alone, especially if the cosmetic change doesn’t bother them. But fungal infections rarely clear up on their own and tend to worsen over time, so earlier treatment generally means a shorter road to a normal-looking nail.