Nail Fungus (Onychomycosis)

Onychomycosis is a fungal infection of the nail. The same group of fungi that cause ringworm on the skin can also get under the nail plate, and yeasts and moulds are responsible in some cases. The infection usually begins at the free edge or the side of a nail and moves slowly towards the base. The nail turns white, yellow, brown or grey, thickens, becomes brittle and crumbly, and may start lifting away from the nail bed, with soft powdery debris collecting underneath. Toenails are affected far more often than fingernails, and the big toenail is the usual first target.

Nail fungus is common and it grows more common with age, in people with diabetes or poor circulation, and in anyone who spends long hours in closed shoes in our heat and humidity. Most people ignore it for years because it does not hurt, and because it looks like a cosmetic nuisance rather than an infection. There are two good reasons not to ignore it. First, an infected nail acts as a reservoir that keeps reinfecting the skin of the feet and can spread to other nails and to other people in the house. Second, a thick, deformed nail presses into the surrounding skin and can cause pain, ingrowing and, in someone with diabetes, a break in the skin that turns into a serious foot infection. The other thing worth knowing early is that not every damaged nail is fungal. Psoriasis, lichen planus, repeated injury and other conditions can look almost identical, and treating them with months of antifungal medicine helps no one, which is why confirming the diagnosis before starting a long course matters.

Diagnosis & Treatment

The first step is to confirm that the problem really is fungal. Nail psoriasis, lichen planus of the nail, chronic trauma from footwear, and a few other conditions can produce a thick, discoloured, crumbling nail that is indistinguishable by eye. A dermatologist will examine all twenty nails, look carefully at the skin of the feet, scalp and elsewhere for clues, and may use dermoscopy of the nail. Where confirmation is needed before committing to months of treatment, a clipping of the affected nail along with the debris beneath it can be sent for laboratory examination such as a KOH microscopy, fungal culture or a special stain, and your doctor will explain which is appropriate. Please do not start any antifungal cream or tablet in the days before giving a sample, as this makes the test unreliable.

Treatment falls into two broad categories. Medicated nail lacquers and solutions applied directly to the nail are suitable for early or limited disease affecting a small part of one or a few nails and sparing the base, and they need to be applied regularly for many months. When several nails are involved, when the infection has reached the base of the nail, or when topical treatment has failed, oral antifungal tablets are generally needed, and courses commonly run for around six to twelve weeks for fingernails and three to six months or more for toenails, depending on the medicine chosen. Because these tablets are taken for a long period, your doctor will ask about your other medicines to check for interactions and may advise blood tests to monitor liver function, and they are not suitable for everyone, including during pregnancy. Trimming and thinning down the thickened nail, and treating any accompanying infection on the soles or between the toes, are usually part of the plan, because leaving that skin infection untreated is a common cause of relapse.

The most important thing to understand about nail fungus is the timeline. The medicine works on the new nail forming at the base, but the damaged part of the nail has to grow out before the nail looks normal. A fingernail takes roughly four to six months to grow out fully, and a toenail can take twelve to eighteen months. So even when treatment is working perfectly, the nail will still look abnormal for months after the tablets are finished. Progress is judged by watching healthy, clear nail emerging from the base, not by how the tip looks. Please be honest with yourself about the common mistakes: stopping treatment early because nothing seems to be changing, borrowing leftover tablets from a relative, using an antifungal cream meant for skin on a thick nail, and going back to damp shoes and untreated athlete's foot as soon as treatment ends. It is also fair to say at the outset that no treatment clears every nail, that response is slower in thick nails and in older people, and that recurrence after successful treatment is not unusual, which is why footwear hygiene, keeping the feet dry, changing socks daily, treating skin infection promptly and not sharing clippers are lifelong habits rather than temporary instructions.