“The causes of thickened and yellowed toenails are as follows.
When fungus invades the toenail, infection is easily triggered if the toenail is in an environment that is conducive to fungal reproduction, such as confinement, humidity or higher temperatures.
The fungus invades the surrounding skin and nail plate, affecting the growth of the toenail and promoting the accumulation of keratinous material around it, causing it to thicken and become cloudy; in addition, when the toenail is malnourished, the surface of the toenail loses its lustre and becomes yellow and bumpy, both of which can manifest as thickened and yellowed toenails.”