A brown toenail can be concerning, but it often stems from common, benign causes. Understanding the reasons behind this change can help determine appropriate steps. This article explores potential culprits.
Common Reasons for Discoloration
Fungal infections, known as onychomycosis, are a frequent cause of brown toenails. Microscopic organisms, primarily dermatophytes, yeasts, and molds, can invade the nail plate, leading to discoloration that may appear yellow, black, or brown. These infections can also cause the nail to thicken, become brittle, or crumble at the edges.
Trauma or injury to the toenail is another prevalent reason for brown discoloration. An impact, such as stubbing a toe, or repetitive pressure from ill-fitting shoes can cause blood vessels beneath the nail to rupture. This results in a subungual hematoma, where blood pools under the nail, appearing dark red, black, or brown as it dries and oxidizes. The discoloration will gradually grow out with the nail over several months.
Certain external factors, such as dark nail polishes, can also stain the nail plate a brownish color. Pigments from deeply colored polishes can seep into the porous nail, leaving a temporary stain even after the polish is removed. Similarly, exposure to external dyes from shoes, socks, or certain chemicals might transfer to the nail, causing surface discoloration.
Some medications can lead to changes in nail pigmentation as a side effect. Certain antibiotics, such as minocycline, or specific chemotherapy drugs are known to cause nail discoloration. This change typically resolves once the medication is discontinued, though it can take time for the nail to grow out.
Less Common Explanations
While less frequent, bacterial infections can also contribute to toenail discoloration. Some bacterial strains, like Pseudomonas aeruginosa, can produce pigments that result in a greenish-brown or brownish hue on the nail. These infections often thrive in moist environments and may be accompanied by a foul odor.
Psoriasis, a chronic autoimmune condition, can affect the nails in various ways, sometimes leading to brown discoloration. Nail psoriasis may manifest as oil spots, which are brownish-yellow patches under the nail plate. The condition can also cause pitting, thickening, or separation of the nail from the nail bed.
A rare but serious cause of brown toenail discoloration is subungual melanoma, a type of skin cancer that develops under the nail. This condition typically appears as a single, dark brown or black longitudinal streak that may widen over time. A key sign, known as Hutchinson’s sign, occurs when the discoloration extends from the nail plate onto the surrounding skin or cuticle. Prompt medical evaluation is necessary if melanoma is suspected.
When to Consult a Doctor
Consult a healthcare professional if toenail discoloration persists or worsens without clear explanation. Any accompanying symptoms like pain, swelling, or redness around the nail warrant immediate medical attention. A medical evaluation is also important if the discoloration appears to be spreading rapidly or changing in appearance.
If the brown discoloration extends onto the cuticle or surrounding skin (Hutchinson’s sign), seek professional advice. This sign can suggest a serious underlying condition, such as subungual melanoma. Also consult a doctor if there has been no recent injury to explain the discoloration or if home remedies for suspected fungal infections have been ineffective.
Maintaining Healthy Toenails
Practicing proper foot hygiene is fundamental for preventing toenail discoloration and other issues. This includes washing feet thoroughly with soap and water and ensuring they are completely dry, especially between the toes, to deter microbial growth. Wearing breathable footwear that allows air circulation around the feet can also help.
Trimming toenails correctly, straight across and not too short, helps prevent ingrown nails and trauma. Avoiding repetitive trauma to the nails from ill-fitting shoes or activities can significantly reduce the risk of subungual hematomas. Using clean, sterilized tools for nail care further minimizes the chance of introducing infections. When using dark nail polishes, applying a breathable base coat can help prevent pigment transfer and staining of the nail plate.