Understanfing the Root Causes of Fingernail and Toenail Infection

Paronychia, a Common Condition With Different Causes

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Paronychia is an infection of the layer of skin surrounding the nail (known as the perionychium). It is the most common hand infection in the United States and is seen frequently in children as a result of nail biting and finger sucking.

The condition can be classified as either acute (rapidly progressing with a short duration) or chronic (ongoing and persistent), depending on the amount of time the infection has been present.

The Causes of Paronychia

Both acute and chronic paronychia start with the penetration of the outer layer of skin called the epidermis.

Acute paronychia is usually the result of a direct trauma to the skin, such as a cut, hangnail, or ingrown nail. Bacteria are most common cause of the infection, predominately Staphylococcus aureus but also certain strains of the Streptococcus and Pseudomonas bacteria.

By contrast, chronic paronychia is most frequently caused by repeated exposure to water containing detergents, alkali, or other irritants. This can lead to the swelling and gradual deterioration of the epidermal layer. Unlike acute paronychia, most chronic infections are caused by the fungus Candida albicans and other fungal agents.

What Paronychia Looks Like

Acute paronychia starts as a red, warm, painful swelling of the skin around the nail. This may progress to the formation of pus that separates the skin from the nail.

Swollen lymph nodes can also develop in the elbow and armpit in more severe cases; nail discoloration can also occur.

In chronic paronychia, the redness and tenderness are usually less noticeable. The skin around the nail will tend to look baggy, often with the separation of the cuticle from the nail bed.

The nail itself will often become thickened and discolored with pronounced horizontal grooves on the nail surface. There may even be green discoloration in cases of Pseudomonas infection.

How Paronychia Is Diagnosed 

Acute paronychia is typically diagnosed based on a review of the clinical symptoms. If there is a pus discharge, your doctor may perform a bacterial culture for a definitive diagnosis. (In all but the most severe cases, this may not be considered necessary since the bacteria will usually be either a Staphylococcus or Streptococcus type, both of which are treated similarly.)

Chronic paronychia tends to be more difficult to diagnose. A potassium hydroxide (KOH) test, in which a smear is extracted from the nail fold, can sometimes confirm a fungal infection. If pus is involved, a culture is usually the best way to confirm the presence of fungus or other, less common infective agents.

The Best Way to Treat Paronychia

In the event of an acute infection, soaking the nail in warm water three to four times a day can promote drainage and relieve some of the pain. Some doctors will even suggest an acetic acid soak, using one part warm water and one part vinegar. If there is pus or an abscess, the infection may need to be incised and drained.

In some cases, a portion of the nail may need to be removed.

Bacteria-associated paronychia is most commonly treated with antibiotics such as cephalexin or dicloxacillin. Topical antibiotics or anti-bacterial ointments are not considered an effective treatment.

Chronic paronychia, by contrast, will typically be treated with a topical antifungal medication such as ketoconazole cream. A mild topical steroid may also be used in addition to the antifungal to help reduce inflammation. (Steroids, however, should never be used on their own as they are unable to treat the underlying fungal infection.)

People with the following conditions tend to have more extensive paronychial infections and may need to be treated with a prolonged course of antibiotics:

  • A compromised immune system, such as with people living with HIV
  • Long-term corticosteroid use
  • Diabetes
  • Autoimmune disease, including psoriasis and lupus
  • Poor circulation in the arms or legs

Ways to Prevent Paronychia

There are a number of precautions one can take to reduce the risk or severity of a paronychial infection:

  • Do not bite nails or trim them too closely.
  • Never bite or cut cuticles.
  • Ensure that your manicurist always uses sterile instruments.
  • Try not to suck fingers.
  • Wear waterproof gloves when immersing your hands in detergents, cleaning fluids, or strong chemicals.
  • Avoid soaking your hands in water for prolonged periods time (or, again, use waterproof gloves).
  • Wash your hands with antibacterial cleanser if you get cuts or scrapes, and bandage, if necessary.
  • Dry your feet off thoroughly if they are immersed for long periods of time in unclean water or water containing detergent or chemicals.
  • Change your socks regularly and use an over-the-counter foot powder if your feet are prone to sweatiness or excessive moisture.

Source

  • Shafritz, A. and Coppage, J. "Acute and Chronic Paronychia of the Hand." Journal of the American Academy of Orthopaedic Surgeons. March 2014;22(3):165-178.

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