Black discoloration on both sides of the fingernails, as if dirty

Under normal circumstances, black discoloration on both sides of the fingernails resembling dirt may be caused by excessive friction, nail trauma, endocrine disorders, chronic paronychia, or onychomycosis. Patients should promptly visit a hospital and receive treatment under medical guidance. Specific analyses are as follows:

1. Excessive Friction

If fingernails are subjected to prolonged friction, continuous external wear and tear may lead to black discoloration on both sides of the nails. It is recommended to take protective measures in daily life, such as wearing gloves, to prevent mechanical friction.

2. Nail Trauma

If the fingernail suffers injury or compression, blood vessels or tissues may be damaged, leading to blood accumulation under the nail (subungual hematoma), which causes the aforementioned symptoms. It is recommended that patients follow medical advice to apply ice packs for symptom relief, but care should be taken not to apply ice for too long—generally limited to 5–10 minutes.

3. Endocrine Disorders

This condition is often associated with factors such as chronic sleep deprivation and poor dietary habits, which may lead to pigmentation and vascular blockage, resulting in symptoms including black discoloration on both sides of the fingernails and purple skin streaks. Patients may follow medical advice to use herbal medications such as Jia Wei Xiao Yao Wan, Wu Ji Bai Feng Wan, or Yi Mu Cao Granules to improve symptoms.

4. Chronic Paronychia

Chronic paronychia is usually related to nutritional deficiencies or fungal infections. Under inflammatory stimulation, symptoms such as nail pain, redness and swelling around the nail, and nail discoloration may occur. It is recommended to follow medical advice and apply topical medications such as mupirocin ointment, fusidic acid sodium ointment, or ketoconazole cream to alleviate symptoms.

5. Onychomycosis (Fungal Nail Infection)

This condition is generally caused by fungal infection and commonly leads to nail plate discoloration, deformation, and thickening, possibly accompanied by pain around the nail groove. Patients may follow medical advice to use antifungal treatments such as terbinafine hydrochloride spray, itraconazole ointment, or ciclopirox olamine cream as adjunctive therapy. Additionally, maintaining nail hygiene in daily life is important; avoid sharing personal items such as slippers or towels with others.

Patients should pay attention to nail hygiene and cleanliness, and avoid injuries to prevent infections.