Causes of Lichen Planus

The exact cause of lichen planus is not fully understood, but several factors are thought to contribute:

Autoimmunity: Genetic predisposition may play a role in triggering an abnormal immune response.
Medications: Certain drugs can induce lichen planus, including:
- Antimalarials (e.g., quinacrine)
- Nonsteroidal anti-inflammatory drugs (NSAIDs)
- Gold salts
- Beta-blockers
- Diuretics
Infections: Viral infections, particularly hepatitis C, have been linked to lichen planus.
Vaccinations: Some vaccines may trigger the condition.
Dental Restorative Materials: Allergies to dental materials like amalgam can lead to oral lichen planus.
Allergens and Contact Sensitivity: Exposure to chemicals or metals can cause allergic reactions.

Triggering and Aggravating Factors

Several factors can worsen or trigger lichen planus symptoms:

Post-Inflammatory Hyperpigmentation: Common after skin lesions heal, leading to dark patches.
Scarring Alopecia: Hair loss due to inflammation, especially in scalp lichen planus.
Nail Dystrophy: Changes in nail appearance, such as ridges or pitting, which can precede or accompany mucosal lichen planus.
Malignant Transformation: Rarely, severe cases may develop into squamous cell carcinoma.