Traveling. Changes in environment—humidity, weather, and even minerals or fluoride in water—can trigger breakouts. There's nothing you can do about the heat index, of course. But wash your face with bottled water when you can, and avoid using hotel soaps.
Stress. It triggers heightened levels of androgens, hormones that contribute to adulthood breakouts. Stress also releases cortisol and other adrenal steroids that can stimulate the sebaceous glands and lead to acne flare-ups, Shamban says. Though it doesn't always cause new cases of acne, stress tends to worsen matters in those already struggling with the condition. Make sure to get enough sleep, and allot 15 minutes each day to relaxing or doing something you enjoy. Squeeze in some exercise, too, since research suggests it helps deflate stress.
Hair-styling products. It's called pomade acne: Breakouts caused by hair gel or any other styling staple. These cause oil to seep onto your forehead, trapping acne-causing bacteria in your pores. Apply products with your hands, keeping them away from the hairline, and wipe your skin with facial cleanser to remove any remaining traces. Be wary of bangs, too, since they bring hair products directly against your forehead.
Chin straps. Bikers and athletes who wear helmets are prone to this type of acne, caused when straps rub against the skin. "Wash your face before and after putting it on, and keep the strap clean," Fusco says. She also recommends using an antibacterial pad to wipe straps down before and after use.
Anti-aging creams. Think you're doing your skin a favor? Think again. Many of these contain retinol, which stimulates cell turnover, increasing the number of acne-like lesions. "Too much turnover can cause a traffic jam in the skin layers," Krant says. Though Retin-A, which contains retinol, is sometimes prescribed to treat acne, experts warn that many people find it to be a skin irritant; plus, anti-aging creams tend to be oily. "Always use these sparingly, and ideally, under a dermatologist's instruction."