Which of the following is a primary cause of an external effect on the skin?

• A. Genetics
• B. Sun exposure
• C. Misuse of products
• D. Diet

Answer: (C)

External effects on the skin come from substances or exposures that act on the surface. When products are misused, their ingredients can irritate or sensitize the skin, damage the protective barrier, and produce surface reactions such as redness, itching, stinging, dryness, or breakouts. These are direct, surface-level responses to external contact with substances, making product misuse a primary external trigger in this context. Genetics and diet influence skin from within and aren’t external surface triggers, while sun exposure is also external but represents a different pathway (UV-driven changes) rather than the immediate surface reaction described here.