Dr. Kaye reveals surprising habit causing embarrassing yellow toenails.

Many people suffer from embarrassing, crusty, yellow toenails. A surprising habit often triggers this issue, and there is a clear way to fix it, according to Dr. Philippa Kaye.

As the sun returns, so do our feet. Winter boots and thick socks give way to sandals and flip-flops, suddenly exposing our toenails. For many patients, this is a source of embarrassment. They feel ashamed and visit the surgery asking for solutions regarding their thickened, discolored nails.

You are not alone in this struggle. Approximately one in ten people has a fungal toenail infection. By age 70, that figure rises to roughly half of all adults.

The usual cause is a family of fungi called dermatophytes. These are the same organisms responsible for athlete's foot. They invade the nail and the skin beneath it. If left untreated, the nail becomes thickened and discolored, often turning yellow, white, or brown. The nail also becomes brittle and can sometimes cause pain.

Why do so many people get infected? Fungal infections become more common with age because nails grow more slowly. You are also at higher risk if you have a weakened immune system or poor circulation, perhaps due to diabetes. Previous nail damage also increases susceptibility. Walking barefoot in communal areas like gym changing rooms or swimming pools increases your initial exposure to the fungi.

However, the surprising factor is often your footwear.

Fungi thrive in warm, dark, and moist environments. The inside of a shoe provides the perfect breeding ground. Synthetic trainers worn for hours, rubber-soled boots, and tight shoes without ventilation trap heat and sweat. This creates the dampness fungi love. This is why Crocs or other sandals are excellent anti-fungal options. Their holes allow air to circulate and help evaporate sweat, preventing moisture buildup.

Your socks also matter significantly. Synthetic sports fibers or merino wool pull sweat away from the skin, allowing it to evaporate. Cotton, on the other hand, acts like a sponge. It absorbs moisture and holds onto it, keeping your feet constantly damp.

You should change your socks daily. This is not obvious advice to everyone. You should also alternate your shoes so each pair gets 24 hours to dry out fully.

This advice only helps those who have not yet contracted the infection. So what do you do once your nails are already crusty and yellow?

The good news is that antifungal nail lacquers, such as amorolfine, are available over the counter. This is where most people go wrong. I see the same mistakes again and again.

Consider my patient Lucy. She noticed athlete's foot, a scaly, itchy rash between her toes a few months ago and did not treat it. Later, her pharmacist diagnosed a fungal toenail infection and recommended an antifungal lacquer. She used it for a month, then came to see me complaining she had wasted her money because it had not worked.

Do you have any of these conditions?

The problem is that a month is not nearly enough time for the lacquer to take effect. This is the most common reason I see for these treatments failing: people simply have not given them long enough.

The reason it takes so long is that toenails grow very slowly. Depending on the specific nail, it can take 12 to 18 months to grow out fully. Amorolfine needs to be applied once or twice a week for at least nine to 12 months. The infected part of the nail may never look better. Crucially, treatment has worked if new, healthy nail grows in from the base.

There is a second mistake I also see.

Patients often make the critical error of failing to file the nail before applying treatment. For antifungal lacquer to be effective, the medication must penetrate the nail plate to reach the fungus residing beneath. When an infection causes the nail to thicken, the drug cannot pass through, rendering the therapy ineffective. This is why treatment kits include disposable nail files; patients must file down the nail before each application. Skipping this step significantly reduces the likelihood of a successful outcome.

A second common mistake involves neglecting athlete's foot. If a fungal infection is present on the skin of the feet, the same pathogen may be responsible for both the skin condition and the nail infection. Treating the nail while ignoring the skin leads to reinfection. Over-the-counter creams designed for athlete's foot should be used in conjunction with nail treatments to address the source of the infection.

Even when patients adhere to these protocols consistently over an extended period, the infection may persist. In such cases, a GP should be consulted. Medical professionals can send nail clippings to a laboratory to identify the specific type of fungus. Based on these results, doctors may prescribe potent terbinafine tablets. While these oral medications are generally more effective and faster-acting than topical solutions, they carry the risk of liver side effects, require medical monitoring, and are not suitable for every patient.

Some private podiatrists offer laser therapy to destroy the fungus, though this option can be costly and results vary. There are also alternative treatments that many patients are unaware of, such as tea tree oil. Some evidence suggests that applying undiluted tea tree oil to the affected nail twice daily after filing may provide benefits, particularly for early-stage infections. Although it requires patience and is less likely to resolve longstanding or severe cases, it can be used alongside standard antifungal lacquers.

Conversely, apple cider vinegar is frequently marketed as a cure for toenail fungus, yet there is no robust scientific evidence supporting its efficacy; it is better reserved for culinary uses. Patients should also avoid covering the infection with regular nail varnish. While understandable, painting over the problem traps moisture, prevents antifungal agents from penetrating the nail, and masks the condition, potentially allowing the infection to worsen unnoticed.

The most effective approach is to keep foot care simple. After washing, feet should be dried thoroughly, including the spaces between the toes. Toenails should be trimmed straight across. Sharing towels, nail clippers, or footwear should be avoided to prevent spreading the infection. If athlete's foot is detected, it should be treated immediately with an over-the-counter cream to prevent it from advancing to the nails. If a fungal toenail is noticed recently, treatment should begin without delay. While patients should not expect immediate results by the summer, following these steps offers a realistic chance of recovery by the time the following year's heatwaves arrive.