LED stands for light emitting diode, a light source that shines on (and penetrates into) the skin. Different wavelengths of light can be used—blue and red being the most common. The light penetrates into the skin and affects gene expression and cellular function leading to a variety of effects in the skin. LED devices often offer an assortment of different light colors based on your skin’s needs. Blue LED light treats acne by killing acne-causing bacteria. Green and yellow LED light treat sensitivity and uneven skin color. Red LED light stimulates collagen and elastin, which can help with anti-aging.