A fungal nail infection — known medically as onychomycosis — is one of the most common nail problems seen in UK practice. It rarely causes serious harm, but it can be uncomfortable, difficult to shift, and a source of self-consciousness. The single biggest thing to understand before you start is that treatment works slowly: the medicine deals with the fungus, but you only see a normal nail once fresh, healthy nail has grown out to replace the damaged part. This guide explains what the infection looks like, the topical and oral options used in the UK, realistic timelines, and when it is worth seeking clinical advice.
What a fungal nail infection looks like
Fungal nail infections usually start at the edge or tip of a nail and work inward. Typical signs include discolouration — white, yellow, green or brown patches — along with thickening of the nail, a crumbly or brittle texture, and sometimes the nail lifting away from the nail bed. Toenails are affected far more often than fingernails, and the big toe is a common starting point. It often accompanies athlete's foot, because the same fungi are involved.
Importantly, not every discoloured or thickened nail is fungal. Psoriasis, an old injury, poor circulation, eczema and other conditions can produce very similar changes. This matters because the treatments differ, and because oral antifungal courses are long and, for some medicines, require monitoring. For that reason a clinician may take a small clipping or scraping of the nail to confirm the diagnosis in the laboratory before committing to treatment — particularly when tablets are being considered.
Why nails get infected and who is more at risk
The fungi responsible are usually the same dermatophytes that cause athlete's foot, which is why the two so often go together. They thrive in warm, damp, enclosed conditions — exactly the environment inside shoes worn for long periods. Once the fungus gets a foothold under or within the nail, the hard, slow-growing nail plate makes it hard to dislodge, which is part of why these infections are so persistent.
Some people are more prone than others. Increasing age, repeated minor nail trauma (common in runners and people who wear tight footwear), heavy sweating, walking barefoot in communal showers or pool areas, and untreated athlete's foot all raise the risk. Health conditions matter too: diabetes, peripheral arterial disease and a weakened immune system not only make infection more likely but also make foot problems in general something to take seriously. Treating any co-existing athlete's foot on the surrounding skin at the same time as the nail reduces the chance of the nail simply being re-infected later.
Topical treatment — amorolfine lacquer
Where the infection is superficial or limited to the end of one or two nails, a topical antifungal applied directly to the nail may be enough. In the UK, amorolfine nail lacquer is a commonly used option. It is painted onto the affected nail once or twice weekly after gently filing the surface, and it works by reaching the fungus through the nail plate over time.
The key limitation is penetration. A lacquer cannot reliably reach fungus that has spread deep into the nail or is affecting the growing area at the base (the matrix). So topical treatment tends to be reserved for early, distal or superficial disease, and it demands patience and consistency — often many months of regular application. Where more of the nail is involved, or where several nails are affected, a clinician may advise that an oral antifungal is a more suitable choice.
Oral treatment — terbinafine
When treatment is needed for more established infection, an oral antifungal is usually first-line in the UK. Terbinafine, typically taken as a 250mg tablet once daily, is the medicine most often used. Because it is carried in the bloodstream and incorporated into the growing nail, it reaches parts of the nail that a lacquer cannot. Courses are usually around six weeks for fingernails and about 12 to 16 weeks for toenails, reflecting how much longer toenails take to grow.
Where terbinafine is not suitable, other oral antifungals such as itraconazole may be considered for some patients, sometimes given as intermittent "pulse" courses. Oral antifungals are prescription-only for good reason: they can affect the liver, may interact with a number of common medicines, and are not appropriate for everyone. A UK-registered clinician will review your medical history, current medicines and any relevant blood tests before deciding whether an oral antifungal is right for you.
How long treatment and nail regrowth take
This is where expectations most often go wrong. Finishing the tablets or lacquer does not mean the nail immediately looks normal. The medicine clears the fungus, but the visibly damaged nail has to grow out and be replaced by healthy nail — and nails grow slowly. Even after a successful course, full visible clearance commonly takes around 9 to 12 months for a fingernail and up to 12 to 18 months for a toenail.
A useful sign of progress is clear, healthy nail appearing at the base and pushing the discoloured portion toward the tip over the months that follow. If there is genuinely no new healthy nail growing through several months after treatment, it is worth asking a clinician to review — the diagnosis may need revisiting, or a different approach considered. Keeping nails trimmed, feet dry, and footwear breathable can support recovery and reduce the chance of the infection returning.
A few practical habits make relapse less likely once you have put in the months of treatment. Dry your feet thoroughly after washing, especially between the toes; alternate your shoes so each pair can dry out; and change socks daily, choosing breathable materials. Avoiding walking barefoot in communal changing rooms and treating any returning athlete's foot promptly both help, because re-infection from the surrounding skin is a common reason a cleared nail becomes affected again. There is no need to throw away footwear, but an antifungal foot powder or spray is a reasonable step some people find useful. None of this is a substitute for treating the infection itself — it simply protects the healthy nail you have worked to grow.
When to seek clinical advice
It is sensible to seek advice before starting treatment rather than after, so that the diagnosis is confirmed and the right option is chosen from the outset. This is particularly important if you have diabetes, poor circulation or a weakened immune system, where nail and foot problems need closer attention. You should also seek review if the surrounding skin becomes red, painful, swollen or starts weeping, as that can suggest a separate bacterial infection.
UK guidance from bodies such as NICE frames onychomycosis as a condition where confirming the diagnosis and weighing the length and risks of treatment against the impact of the infection is central. In practice that means treatment is not automatic — a small, painless patch on one nail may reasonably just be monitored, while painful, spreading or multi-nail disease is more likely to warrant active treatment.
Working with your Farmeci clinician
A consultation typically covers how long the nail has been affected, how many nails are involved, whether you have athlete's foot, your general health and any medicines you take. From there, a clinician can advise whether a topical lacquer, an oral antifungal, or simply monitoring is the most appropriate step for you, and whether a nail sample would help confirm the cause first. If you would like to understand more about long-term skin and nail conditions, our Skin & Hair guides cover related topics, including how the topical-versus-oral treatment ladder is used in our guide to acne treatment and our overview of scabies treatment.