Onychomycosis - Symptoms, Causes & Treatment
By ScanSkinAI Editorial Team✓ Reviewed for medical safetyLast updated June 2026
A fungal infection of the nails causing thickening, discoloration, and crumbling. It affects toenails more than fingernails.
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Quick Answer
Onychomycosis is a common fungal infection that primarily affects the toenails, though it can also occur on fingernails. The infection typically causes the nail to become thick, discoloured (often yellow, brown, or white), and brittle or crumbly at the edges. It thrives in warm, moist environments and is more common if you have suffered nail trauma or have poor circulation. While it can be stubborn to treat, options range from medicated nail lacquers to oral antifungal medications. Always consult a healthcare professional for an accurate diagnosis and treatment plan.
Symptoms
- Thickened nails
- Yellow, brown, or white discoloration
- Brittle, crumbly edges
- Distorted shape
- Debris under nail
- Foul odor
Causes & Risk Factors
- Dermatophyte fungi
- Yeast
- Molds
- Warm, moist environments
- Nail trauma
- Poor circulation
Treatment & Management
- Oral antifungals (terbinafine, itraconazole)
- Topical antifungals
- Ciclopirox nail lacquer
- Laser therapy
- Nail removal
When to See a Doctor
If nails are thickened and discolored, especially if you have diabetes
Frequently Asked Questions
What does a fungal nail infection look like?
Early signs often include a small white or yellow spot under the tip of your nail. As the fungal infection goes deeper, the nail may become thickened, noticeably discoloured, and distorted in shape. You might also notice the edges becoming brittle or crumbly, a buildup of debris trapped under the nail bed, or a slightly foul odour.
How did I get nail fungus?
Nail fungus is usually caused by dermatophyte fungi, though yeasts and moulds can also be responsible. These organisms thrive in warm, moist environments, such as sweaty shoes, public swimming pools, and gym locker rooms. You are more likely to develop an infection if you have a history of nail trauma, poor circulation, or immune system issues.
How do you get rid of a fungal nail infection?
Because the fungus lives deep inside the nail bed, it can be stubborn to eliminate. Treatment options depend on severity but often include prescription oral antifungal tablets like terbinafine or itraconazole. More mild cases might be managed with topical antifungal creams or medicated nail lacquers such as ciclopirox. In very severe or painful cases, laser therapy or partial nail removal might be recommended by a doctor.
How long does it take for nail fungus to go away?
Fungal nail infections require quite a bit of patience to clear. Even with effective prescription treatments, the existing damaged nail does not heal. Instead, you must wait for a completely new, healthy nail to grow out. For fingernails, this process usually takes about six months. For toenails, it can take up to a year or longer to see completely clear results.
When should I see a doctor about my thickened toenails?
You should consult a healthcare provider if your nails become increasingly thickened, painful, or significantly discoloured. It is especially important to see a doctor promptly if you have diabetes, a weakened immune system, or poor circulation. In these cases, even a seemingly minor foot or nail infection can quickly lead to more severe, widespread health complications if left untreated.
How can I prevent spreading or getting nail fungus again?
Keeping your feet clean and dry is the best defence. Wear shoes that breathe well and change your socks daily, especially if your feet sweat heavily. Avoid walking barefoot in public areas like locker rooms or communal showers. Keep your nails trimmed straight across, disinfect your nail clippers regularly, and avoid sharing towels or footwear with someone who has an active fungal infection.
Is a yellow nail always caused by a fungal infection?
Not necessarily. While a fungal infection is a very common reason for yellow, thick nails, other conditions can cause similar changes. Psoriasis, ordinary nail trauma, ageing, and certain medical conditions or medications can also alter the appearance of your nails. This is why a professional medical evaluation, sometimes involving a nail clipping test, is necessary to confirm the exact root cause before starting any treatment.
How can ScanSkinAI help with onychomycosis?
ScanSkinAI can analyze photos of your nails to help identify visual patterns commonly associated with onychomycosis, such as discolouration or thickening. However, it is strictly a screening aid and cannot provide a definitive medical diagnosis. Because other conditions like nail psoriasis look very similar, you should use the app's insights to guide a conversation with a doctor, who can confirm the cause and prescribe treatment.
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Medical References
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Medical Disclaimer: This information is for educational purposes only and is not intended as medical advice. The content on this page should not be used to diagnose or treat any health problem. Always consult with a qualified healthcare professional for proper medical evaluation, diagnosis, and treatment of your condition.