The biggest threat to skin indoors is dry heat. If you control the heat inside your home or office, Biro recommends turning it down; if you can't control it, open a window, or better yet, get a humidifier. Use gentle, soap-free cleansers on your face (1), and be sure to moisturize from hairline to toes every day (2). The most ignominious consequence of dry heat is, of course, winter dandruff. According to Kattia Solano, owner of Butterfly Studio Salon in New York, "Winter dandruff means dry, white flakes with no inflammation or redness on the scalp, as opposed to seborrheic dermatitis-related dandruff, in which the scalp is red or scaly." If you have winter dandruff, a conventional dandruff shampoo – which has ingredients that target the fungus and yeast of seborrheic dermatitis – won't fix it. Instead, to keep flakes outside and off your shoulders, use a moisturizing shampoo (3), a cream treatment, or an oil for your scalp.

Pictured, from left:

1. Coola ER Clear Recovery Foam Wash [$24;]
2. Malin + Goetz Replenishing Face Cream [$72;]
3. Kérastase Dermo-Calm Bain Vital Shampoo [$27;]