Dark Stripes on Tongue: Possible Causes

What Could Cause Dark Lines on the Tongue?

• Geographic tongue – benign, map-like patches with white borders; more common in women.
• Fungal infection (oral thrush) – Candida overgrowth; dark spots/stripes; risk with immunosuppression.
• Vitamin B12 deficiency – pale, smooth, red tongue with dark streaks.
• Smoking – tar/nicotine stain tongue dark brown/black.
• Medication side effects – e.g., antibiotics; usually temporary.

If concerned, see a doctor to rule out underlying conditions.