Paronychia (Nail Fold Infection): Causes and Treatment

What is Paronychia?

Paronychia (or nail fold infection), commonly known as a whitlow or nail infection, is an inflammation that affects the skin around the nail. It is usually accompanied by pain, swelling, redness, and sometimes pus.

This inflammation at the edge of the nail can be caused by bacterial or fungal infections, or by non-infectious irritative processes, and it often develops after some type of injury or trauma to the skin surrounding the nail (the periungual area).

Paronychia is one of the most common skin infections affecting the hands and feet. It can occur on both fingernails and toenails, though it’s more common on the fingers due to their greater exposure to trauma, the habit of nail biting, and more frequent contact with moisture and irritating substances.

Clinically, paronychia is divided into two main types:

Chronic paronychia: Characterized by persistent or recurrent inflammation that lasts for weeks or even months. It’s typically related to repeated exposure to water, irritating chemicals, or allergens. There may also be a secondary infection by bacteria or fungi—especially Candida albicans—but the main underlying issue is usually non-infectious inflammation (known as periungual eczema).
Acute paronychia: Develops quickly, over a few hours or days, usually following a recent injury to the skin around the nail. The most common cause is a bacterial infection, often by Staphylococcus aureus.

How Nail Inflammation Develops

Paronychia occurs when the skin around the nail becomes damaged or weakened, allowing bacteria, fungi, or irritating substances to enter and trigger an inflammatory response.

Basic Mechanism

The skin around the nail acts as a natural protective barrier against microorganisms in the environment. When this barrier is broken—even by tiny, almost unnoticeable cracks—germs that normally live harmlessly on the skin, such as the bacterium Staphylococcus aureus, can penetrate deeper layers and cause a localized infection.

In non-infectious (chronic) forms, the inflammation results from ongoing irritation or contact allergy, which damages the periungual skin and makes secondary infections more likely.

Main Causes

Paronychia can occur in anyone, but certain situations greatly increase the risk. The most common triggers include:

Minor trauma to the nails or cuticles
- Cutting the nails too short or unevenly.
- Aggressively removing cuticles.
- Accidental injuries from manicure or pedicure tools (“cutting the skin around the nail”).
Harmful habits
- Nail biting (onychophagia) or biting the skin around the nails.
- Thumb sucking, a habit more common in children.
Occupational and environmental factors
- Jobs that involve constant contact with water (e.g., laundry workers, cooks, healthcare professionals).
- Frequent handling of irritating chemicals without proper gloves (e.g., detergents, disinfectants).
- Gardening-related jobs, due to direct contact with contaminated soil and small thorns or splinters.
Anatomical and mechanical factors
- Wearing tight shoes that repeatedly injure the toenails.
- Stubbing or hitting the toes (especially the big toe, or hallux).
Associated medical conditions
- Diabetes mellitus, because it affects circulation and the immune response.
- Peripheral vascular problems, which make healing more difficult.
- Immunosuppression (HIV, corticosteroid use, or chemotherapy).

Which Germs Cause Nail Infections?

Paronychia is caused by microorganisms that enter the skin around the nail when the protective skin barrier is compromised. The specific agents vary depending on the type of paronychia (acute or chronic) and how the infection was acquired.

Acute Paronychia: Bacteria

In acute cases, the infection is usually bacterial and develops rapidly.

Staphylococcus aureus – This is the most common culprit. It normally lives on the skin, but when it enters through small cracks, it causes inflammation, intense pain, and pus formation.
Streptococcus pyogenes – Can cause a more widespread inflammation, with diffuse swelling and redness, often without a visible abscess.
Pseudomonas aeruginosa – Less common, but can affect people with prolonged exposure to water. A typical sign is a greenish discoloration in the inflamed area, caused by pigments produced by the bacteria.

Paronychia Linked to Mouth Contact

When the infection occurs after nail biting, thumb sucking, or finger bites, microorganisms from the oral flora can invade the skin. Examples include:

Eikenella corrodens
Fusobacterium (anaerobic)
Peptostreptococcus
Prevotella and Porphyromonas

This type of paronychia can be more severe, as it involves less common skin germs and may require broad-spectrum antibiotics to treat effectively.

Chronic Paronychia: Fungi and Non-Infectious Inflammation

In chronic cases (lasting more than 6 weeks), along with chemical irritation or contact allergy, it is common to find fungal colonization by:

Candida albicans – An opportunistic fungus that thrives in moist environments. Its presence sustains the inflammation and delays healing of the periungual skin.

Important: Not all chronic paronychia is infectious. In many cases, it is actually a form of eczema (either allergic or irritant dermatitis) without any microorganisms involved at first. However, the damaged skin may later become secondarily colonized by bacteria or fungi.

Mixed Infections

Mixed infections are common in chronic paronychia. Initially, the skin becomes inflamed due to chemical irritation or allergy, and is later colonized by Candida and skin bacteria. This combination prolongs the condition and makes it harder to heal.

Symptoms of Paronychia

The symptoms of paronychia vary depending on the type (acute or chronic) and the severity of the inflammation. Recognizing these differences is essential for an accurate diagnosis and for choosing the most appropriate treatment.

Symptoms of Acute Paronychia

Acute paronychia is characterized by a rapid, painful inflammation, usually limited to a single finger.

Main signs and symptoms:

Intense, localized pain that worsens when the finger is touched or pressed.
Swelling (edema) and redness around the nail (periungual erythema).
Local warmth in the inflamed area.
Pus formation (abscess): common at the sides/corners of the nail, visible as a whitish or yellowish spot under the skin.
Difficulty moving the finger due to pain.
Rapid progression: typically peaks within 24 to 48 hours after the initial injury.
Fever is uncommon. When present, it may indicate the infection is spreading to nearby tissues, progressing to erysipelas or cellulitis, especially in people with weakened immunity.

Symptoms of Chronic Paronychia

Chronic paronychia develops more slowly and persists, with milder symptoms that can last for weeks or months.

Main features:

Mild to moderate inflammation around the nail, without obvious pus.
Persistent swelling at the fingertips (a “swollen finger” appearance).
Mild pain or discomfort, especially with pressure on the area.
Nail changes over time: deformities, rippling, ridges, or partial separation of the nail from the nail bed (onycholysis).
May affect several fingers at the same time, usually on the hands.
Worsening after contact with water, chemicals, or repeated trauma.

In cases associated with fungal infection (Candida), the inflammation is usually subtle but persistent, with peeling or whitish skin due to maceration.

Images of nail inflammation

Inflammation and pus under the skin next to the nail.

Inflammation and pus at the corner of the nail.

Paronychia evolving into erysipelas of the finger.

Difference From Other Nail Conditions

It is important to distinguish paronychia from other conditions that affect the nails and fingers, such as:

Onychomycosis (fungal nail infection): a fungal infection of the nail plate that causes thickening, brittleness, and changes in nail color, but it does not typically cause acute inflammation of the skin around the nail.
Felon (deep fingertip infection): a bacterial infection of the fingertip pulp (the soft tissue pad), deeper and more painful than paronychia. It differs because it is not limited to the periungual area (around the nail).
Contact dermatitis: irritant or allergic inflammation of the skin around the nail triggered by chemicals or allergens, without infectious microorganisms being involved.
Ingrown toenail (onychocryptosis): occurs when the edge of the nail grows into the adjacent skin, causing pain and redness and, in more severe cases, a secondary infection that can resemble paronychia. It differs because the primary problem is a localized mechanical injury, related to abnormal nail growth or wearing tight shoes.

Treatment of Paronychia

Treatment for paronychia depends on the type (acute or chronic), the severity of symptoms, and whether there is a bacterial or fungal infection. In both cases, simple local measures and preventive care play a central role in recovery.

Treatment of Acute Paronychia

Acute paronychia, usually caused by bacteria, often responds well to local care. Warm compresses applied three to four times a day help reduce inflammation, relieve pain, and promote spontaneous drainage of small pus collections. Proper cleansing of the area is essential to prevent the infection from worsening.

When there is visible pus or an abscess, drainage is often necessary. In mild cases, soaking the finger in warm water followed by gentle massage may be enough to help the pus drain. However, if the abscess is large or the pain is severe, drainage should be performed by a healthcare professional, in an appropriate setting and using sterile technique, to avoid complications.

In most cases, antibiotics are not needed. However, if there are signs of worsening—such as spreading redness, increasing pain, or fever—oral antibiotics may be indicated to prevent the infection from spreading.

Common options include cephalexin, amoxicillin–clavulanate, and, in cases of allergy or resistance, clindamycin. In specific situations, such as infections related to human bites, antibiotics that cover oral bacteria are recommended.

Patients with diabetes, immunosuppression, or peripheral vascular disease require special attention, as they are at higher risk of complications and may need early medical evaluation.

Treatment of Chronic Paronychia

Managing chronic paronychia requires more patience, because the main goal is to break the cycle of inflammation and ongoing irritation. Avoiding moisture and reducing contact with chemicals are the most effective measures to allow the skin and cuticle to heal. Protective gloves—preferably vinyl gloves with a cotton lining—are recommended for people who frequently handle water or irritating substances.

In addition to protective measures, medium- to high-potency topical corticosteroids, such as betamethasone, help control inflammation when there are no signs of active infection. When fungal colonization is present, topical antifungal creams containing ketoconazole or terbinafine can be used. If the fungal infection is extensive or does not respond to topical therapy, oral antifungals such as itraconazole or fluconazole may be prescribed.

In recent years, medications such as topical tacrolimus have shown effectiveness in reducing chronic inflammation in cases of periungual dermatitis without associated infection, and can be a useful alternative for patients who need to avoid long-term corticosteroid use.

Full recovery from chronic paronychia may take several weeks to months. During this period, keeping the skin dry, moisturized, and protected is essential to prevent relapses.

Prevention and General Care

Preventive measures are just as important as treatment, especially to avoid recurrences. Keeping the skin of the hands moisturized, avoiding aggressive cuticle removal, and not biting the nails are simple but effective steps. In occupational settings, consistent use of appropriate gloves helps protect against chemical irritants and prolonged moisture. For those who get professional manicures, it is essential to ensure that tools are properly sterilized and that cuticles are not removed excessively.