Dark cuticles on the fingernails or toenails can indicate certain conditions including an infection, according to WebMD. Fungal infection are one of the most causes of cuticles or fingernails turning a dark color.
Fungal infections are treated with medications designed to kill the fungi present. The infections are not serious unless left untreated so medical attention is important.
Other conditions that can cause dark cuticles is bruising of the fingers or toes. If the cuticle darkens, but returns to a normal color within a few days, the likely cause is bleeding or bruising of the nail and surrounding tissues due to an injury.
One uncommon cause of darkened cuticles is skin cancer. Other signs of skin cancer in the fingernail or cuticle region include growth of tissue, pitting or holes on the nails and warts on the nail bed. Since cancer is a very serious medical condition, a person experiencing cuticle discoloration or other issues with the nails should contact a doctor or dermatologist for an accurate diagnosis.
Other rare causes for darkened cuticles include heart disease or kidney problems. Darkened cuticles or fingernails are typically not the first sign or system to appear when a person has one of the medical conditions, however.