When it’s cold outside, we often forget to drink enough water. But hydration is still essential for energy, digestion, immunity, skin health, and even mental clarity. Dehydration in winter can sneak up on you, causing dry skin, fatigue, headaches, and sugar cravings — all things that disrupt your glow. Research from the American Heart Association found that even mild dehydration impairs blood vessel function almost as much as smoking a cigarette, and has been linked to inflammation and increased risk of heart disease.