A fingernail infection, medically known as paronychia, appears as red, swollen tissue around the nail, often with pus buildup and tenderness. It may start at the cuticle or along the nail's side and progress rapidly if untreated. The condition can be acute (developing over hours to days) or chronic (lasting weeks to months).
Acute paronychia usually begins with localized pain and warmth. The skin near the nail becomes inflamed and may bulge. Pus collects under the nail or in the fold, creating a visible pocket of fluid. As pressure builds, the area feels throbbing and sensitive to touch. In severe cases, the nail detaches from the nail bed.
Chronic paronychia develops slowly. The skin stays mildly swollen and red for longer periods. The cuticle may peel or split. Pus is less common, but the area remains tender. This form often results from repeated exposure to moisture or irritants, such as frequent hand washing or working with water.
The earliest sign is redness and swelling along the nail fold-the area where the nail meets the skin. This region becomes warm and painful. Within 24 to 48 hours, a small blister may form filled with clear or cloudy fluid. If bacteria invade, the fluid turns yellow or green and thickens into pus.
As the infection worsens, the nail may lift slightly from the nail bed. A visible collection of pus under the nail edge is a strong indicator of advanced infection. In some cases, the nail itself changes color-turning yellow, green, or black due to trapped debris or blood.
One patient I treated had a swollen index finger after trimming a hangnail. By day two, the entire nail fold was red and firm. A small bump of pus appeared at the base of the nail. After draining it in clinic, the swelling resolved within 48 hours. This case illustrates how quickly acute infections can escalate.
There are two primary forms: bacterial and fungal. Bacterial paronychia is the most common and typically caused by Staphylococcus aureus or Streptococcus species. It presents suddenly with intense pain, heat, and purulent discharge. Fungal paronychia develops gradually and is linked to Candida albicans. It causes persistent swelling, thinning of the nail, and sometimes a whitish or yellowish discharge.
Many mistake early signs for minor irritation or a hangnail. Redness that spreads beyond the nail fold, especially with fever or worsening pain, signals a deeper infection. Another error is treating it with home remedies like tea tree oil or vinegar soaks without addressing the underlying cause. These can delay proper treatment and increase risk of complications.
Fungal infections are often misdiagnosed as bacterial. They don't usually cause sudden pain or pus. Instead, they lead to gradual nail thickening, discoloration, and crumbling. If left untreated, they can permanently damage the nail matrix-the tissue that grows the nail.
| Type | Onset | Appearance | Common Cause |
|---|---|---|---|
| Bacterial (acute) | Sudden (hours-days) | Red, swollen, hot, pus-filled | Staphylococcus aureus, Streptococcus |
| Fungal (chronic) | Gradual (weeks-months) | Swollen, thickened nail, peeling cuticle | Candida albicans |
See a healthcare provider if swelling extends past the nail fold, pus drains spontaneously, or pain limits daily function. Signs of systemic infection-fever, chills, or red streaks spreading up the finger-require urgent attention. Delaying care increases the risk of bone infection (osteomyelitis), which can lead to permanent disability.
For mild cases, soaking the finger in warm salt water (1 teaspoon salt per cup of water) for 15 minutes, three times a day, may reduce swelling. However, this does not replace medical evaluation. Over-the-counter pain relievers like ibuprofen help manage discomfort but do not treat the infection.
If the infection persists beyond five days or worsens, antibiotics are likely needed. Oral antibiotics such as dicloxacillin or cephalexin are prescribed for bacterial cases. Topical antifungals like clotrimazole are used for fungal infections. In severe cases, surgical drainage may be required.
Paronychia is often confused with ingrown nails. An ingrown nail presses into the skin and causes pain, but it lacks pus and widespread redness. It typically affects the outer edge of the nail and may show a small, sharp piece of nail growing into the flesh.
Another confusion arises with subungual hematoma-blood under the nail from trauma. This appears as a dark purple or black discoloration that doesn't change with pressure. Unlike infection, it's not warm or painful unless pressure builds. The nail may eventually fall off, but no pus forms.
Keep hands dry and avoid biting or picking at cuticles. Wear gloves during wet work. Trim nails straight across-not too short-to prevent injury. If you have diabetes or poor circulation, monitor fingers closely for any signs of infection.
Early intervention prevents progression. If you notice redness, swelling, or pain near the nail, do not ignore it. Prompt treatment reduces recovery time and avoids complications.
Understanding what a fingernail infection looks like helps catch it early. Recognizing the difference between acute bacterial, chronic fungal, and traumatic causes ensures accurate care. Always consult a provider if symptoms persist or worsen.