Actinic keratosis is caused by...

• A. Bacterial infection
• B. Chemical exposure
• C. Sun exposure or aging
• D. Trauma

Answer: (C)

Actinic keratosis arises from cumulative sun damage: ultraviolet light harms the DNA of skin cells over time, and this damage accumulates as we age, leading to the rough, scaly patches characteristic of the condition. That connection to sun exposure and aging is why this is the correct cause. Bacterial infection doesn’t produce these UV-driven changes, chemical exposure can cause other skin problems but not the specific UV-induced keratinocyte alterations, and trauma isn’t what creates the sun-damaged changes seen in actinic keratosis.