Just as they say, ‘your eyes are the mirror of the soul’, so too are your toenails mirrors of your health – revealing information about nutritional status, general health and even an undiagnosed systemic disease.
The primary cause may be from trauma – either from an object dropped onto the toenail or from constant bumping inside a shoe, as suffered by runners and athletes. This discolouration is due to micro-bleeding under the nail, and will grow out with the nail over a period of months (it can take eight to 10 months for the big toenail to grow out completely). If severe bleeding occurs under the nail, the nail may detach while a new nail grows out, provided there is no damage to the nail matrix or the nail bed.
In some instances, in women who have dark skins, it may be perfectly normal for aging to bring about brown or black streaks in the toenails. These are due to changes in melanin (the natural pigment that causes skin and nail darkening).
Changes in consistency, curvature, surface texture, growth and even colour can be signs of a systemic process. For example, blue half-moons or lunulae on your toenails can indicate Wilson’s disease of the liver or silver salts deposition in argyria. In rare instances, discolouration can indicate the presence of a benign glomus tumour beneath the nail, or, even more rarely, malignant melanoma.
Extremely thick toenails (onychogryphosis)
Poor circulation in the feet affects blood supply to the nail matrix and nail bed. It is thought that the stop-start nature of poor circulation (intermittent hyperaemia) triggers the cell replication that can result in thickened toenails. Poor circulation can be present in cardiac conditions as well as in people who have high or low blood pressure, diabetes mellitus, or visible broken and/or varicose veins.
Ingrown toenails (onychocryptosis)
- Excessive moisture can cause toenails to bend and penetrate the skin.
- Pressure from shoes or from adjoining toes can shape or mould the toenail into the surrounding skin.
- Growth spurts in childhood and adolescence can result in a toenail that is wider than the growing toe for a period.
- Incorrect cutting of toenails can cause ingrown toenails.
- Fungal infection under the toenail causes weakening of the nail plate and thus structural change in the curvature of the nail, and discolouration. People living with diabetes have an increased risk of fungal infections in the foot.
- Trauma, such as accidentally dropping heavy objects onto the nail bed and/or the nail matrix at the source of the nail, causes a shape change in the resultant nail growth.
Footwear knowledge to prevent discoloured, thick or ingrown toenails
Avoid shoes that are too narrow in the front of the foot as these can restrict blood circulation to your toes.
Shoes that are too tight in the toe area may promote ingrown toenails.
Avoid shoes that have a shallow tapering toe box as these will constantly rub against the tops of your toenails. Toe muscle action is essential in preventing bunions and corns, hence why you should have enough toe room to be able to wiggle your toes inside your shoes.
Choose styles that do not require gripping friction from your toes, such as those that grip around the heel (either closed heel or strap), plus a strap or some form of fastening or closure across the instep of the foot.
Heeled shoes tilt body weight onto the ball of the foot. This can lead to toes curling inside the shoe, possibly resulting in hammer toes. Choose flats or lower heels for everyday use and reserve high heels for short one- to two-hour functions or events.