What causes discoloured toenails?

Toenail discolouration can develop from infections, trauma, medical conditions or lifestyle factors. Understanding the cause helps guide effective treatment.

• Fungal infections — the most common cause of yellow, green or brown nails (onychomycosis), leading to thickened, brittle and discoloured nails.
• Trauma or repeated pressure — bruising under the nail (subungual haematoma) can appear as dark purple or black patches.
• Bacterial infection — Pseudomonas bacteria can turn the nail greenish due to pigment formation under the plate.
• Underlying health or skin disorders — psoriasis, eczema, diabetes or thyroid disease can alter nail colour and texture.
• Chemical or cosmetic staining — long-term nail polish use, dyes or cleaning agents may temporarily stain nails yellow or brown.
• Medications, smoking or poor circulation — these may slow growth or dull nail colour.
• Serious medical conditions — dark streaks that do not grow out may indicate melanoma or other nail-bed disease.

What does toenail discolouration look like?

The appearance varies with the cause:

• Yellow or brown nails — usually due to fungal infection, ageing or nail polish stains.
• White or chalky nails — linked to surface damage or early fungal infection.
• Black or dark purple nails — caused by trauma and bleeding under the nail; persistent pigmentation requires medical review.
• Green nails — bacterial infection giving a greenish hue, sometimes with mild odour.
• Blue or grey nails — may result from poor circulation, low oxygen or certain drug use.

Affected nails may also become thick, brittle, ridged or partially detached from the nail bed. If colour changes persist or spread, seek professional assessment to rule out infection or other nail-bed disorders.

Who is more likely to develop discoloured toenails?

Some individuals are more prone to toenail discolouration due to lifestyle or health factors:

• Athletes and active individuals: Repeated impact or pressure on the toes during sports and exercise can lead to toenail bruising or thickening.
• People who wear tight or enclosed shoes: Prolonged pressure from tight footwear may cause bruising, while moisture trapped inside enclosed shoes creates an ideal environment for bacterial or fungal infections.
• Older adults: Reduced circulation and slower nail growth make nails more vulnerable to damage and infection.
• Individuals with diabetes or vascular disease: Poor blood flow can delay healing, increasing the risk of nail injury and infection.
• Those with psoriasis or eczema: These chronic skin conditions can also affect the nails, leading to pitting, thickening, or discolouration.

Maintaining good foot hygiene, choosing breathable footwear and managing chronic conditions can lower risk.

How are discoloured toenails diagnosed?

Our podiatrist will assess the nail’s colour, texture and structure to identify the cause.

• Clinical examination — visual inspection for bruising, infection or pigment changes.
• Medical history — review of footwear, injuries, nail care habits and health conditions.
• Nail sampling —  the podiatrist may refer patients to do nail sample testing (e.g. microscopy or culture) to identify the presence of fungi.
• Imaging or biopsy — the podiatrist may refer patients to do a biopsy to exclude melanoma or other underlying conditions.

Accurate diagnosis ensures suitable treatment, be it antifungal therapy, trauma management or investigation of systemic illness.

What are the treatment options for discoloured toenails? 

The treatment for discoloured toenails depends on the underlying cause, severity and whether infection or trauma is involved. Early diagnosis helps guide the right approach and prevents further nail damage or recurrence.

• Nail trimming and debridement — careful reduction of thickened or discoloured nails relieves pressure and improves appearance.
• Laser therapy — targets fungal and bacterial infection within and beneath the nail to restore nail health
• Trauma management — protective footwear and gentle care allow recovery; severe injury may need partial or full nail removal.
• Addressing health and lifestyle factors — managing diabetes, psoriasis or circulation problems supports healthy nail regrowth.

Professional evaluation ensures that the right treatment is chosen based on the cause, leading to faster healing and long-term improvement in nail appearance.

Summary

Discoloured toenails may result from fungal or bacterial infection, trauma or systemic conditions like diabetes and psoriasis. The nails can appear yellow, brown, black, green or white and may also thicken or lift from the nail bed. While mild changes can be cosmetic, persistent or spreading discolouration should be examined by a podiatrist to rule out infection or nail-bed disease.

Diagnosis involves clinical assessment and laboratory testing where necessary. Treatments include nail care, antifungal or antibacterial laser therapy or nail removal, depending on the cause. Preventive measures such as proper hygiene, use of breathable footwear and early care for minor infections can help maintain healthy, natural-looking nails.

If you notice persistent nail discolouration, thickening or discomfort, schedule a consultation with Atlas Podiatry for a professional assessment and personalised treatment to restore the natural health and appearance of your toenails.