Fungal nail infections - also known as onychomycosis - are common conditions that affect the toenails and fingernails. Fungal organisms like dermatophytes, yeasts, or moulds can invade the nail bed. This leads to thick, discoloured, and brittle nails. Left untreated, a fungal nail infection can spread and lead to pain, discomfort and nail deformity.

As podiatrists, we often see patients with ongoing nail infections. Many of them are unsure about the cause or the best treatments. Knowing the different types of fungal nail infections can help you spot the problem early. This way, you can choose the best treatment.

What Causes Fungal Nail Infections?

Fungal nail infections develop when fungi enter small cracks in the nail or surrounding skin. This can happen due to:

  • Warm, moist environments – Fungi thrive in damp conditions, making public pools, gyms and showers high-risk areas.
  • Injured nails – Cracks, trauma, or damage to the nail can allow fungal spores to take hold.
  • Sweaty feet – Excess moisture trapped in socks and shoes encourages fungal growth.
  • Weakened immune system – Those with diabetes, circulatory problems or weakened immunity are more prone to infection.
  • Sharing personal items – Using another person’s nail clippers, socks, or shoes can spread fungal spores.

Toe Nail Infection Types

Types of Fungal Nail Infections

1. Distal Subungual Onychomycosis (DSO)

This is the most common type of fungal nail infection, caused primarily by dermatophyte fungi such as Trichophyton rubrum. It usually begins at the tip of the nail and spreads towards the cuticle.

Symptoms:

  • Yellow, white, or brown discolouration at the edge of the nail
  • Thickened, brittle nails that become crumbly
  • Separation of the nail from the nail bed (onycholysis)
  • Often affects one or more toenails

2. Proximal Subungual Onychomycosis (PSO)

This type of nail fungus starts at the base of the nail (near the cuticle) and spreads towards the tip. It is less common but often indicates an underlying immune system issue.

Symptoms:

  • White spots or streaks near the cuticle
  • Thickened, rough nail texture
  • Nail lifting away from the bed

3. White Superficial Onychomycosis (WSO)

WSO affects the surface of the nail - rather than underneath it. It is easier to treat than other types, as it does not penetrate deeply into the nail bed.

Symptoms:

  • Chalky white patches on the nail surface
  • Soft, flaky nails that become brittle
  • No separation from the nail bed (unlike other infections)

4. Candida Onychomycosis (Yeast Infection of the Nail)

Candida fungi can infect nails. This is common in people with wet hands or a history of nail infections. This type is more common in the fingernails than toenails.

Symptoms:

  • Thickened, yellowish nails
  • Swelling and redness around the nail (sometimes with pus)
  • Painful, tender nail bed

How to Prevent Fungal Nail Infections

  • Keep feet clean and dry – Wash daily and dry thoroughly, especially between the toes.
  • Wear breathable shoes – Choose footwear that allows air circulation to prevent moisture build-up.
  • Change socks daily – Use moisture-wicking socks to keep feet dry.
  • Avoid walking barefoot in communal areas – Public showers, swimming pools, and gyms are hotspots for fungi.
  • Trim nails properly – Cut straight across and avoid cutting too short to prevent nail trauma.
  • Use antifungal treatments – These help reduce fungal spores in shoes and socks.
  • Don’t share personal items – Avoid sharing nail clippers, towels, or shoes.

Laser Treatment for Fungal Nail

When to See a Podiatrist

If you notice persistent discolouration, thickening, or nail changes, it's best to seek professional advice. A podiatrist can:

  • Diagnose the type of fungal infection using a nail sample
  • Recommend the most effective treatment based on the severity of infection
  • Provide nail care and advice to prevent recurrence

Fungal nail infections are stubborn but treatable conditions. Identifying the type of fungal infection early and using targeted antifungal treatments can prevent long-term damage. If you have thick, discoloured, or brittle nails, don’t wait. Getting help from a podiatrist is the best way to have healthy, clear nails.