Which of the following is a common trigger for acne flare-ups?

Stress is recognized as a common trigger for acne flare-ups due to its physiological effects on the body. When a person is stressed, the body produces higher levels of hormones such as cortisol, which can lead to increased oil production in the skin. This excess oil can clog pores and create an environment conducive to the growth of acne-causing bacteria. Additionally, stress can also lead to inflammatory responses in the skin, worsening existing acne or precipitating new breakouts.

The other options present factors that are generally beneficial to skin health. Increased outdoor activity can improve circulation and promote skin health, a consistent sleep schedule is associated with better overall health and can aid in the repair and regeneration of skin, and drinking more water helps to keep the skin hydrated, potentially improving its appearance and health. In this context, these activities would not typically exacerbate acne, unlike stress.