Just like your own hair, hair extensions need to be conditioned after shampooing to maintain a healthy shine and promote styling ease. Place a small amount of conditioner free of silicone, parabens and sulfates on your hand, then gently work the conditioner into the hair extensions. Let the conditioner sit for three to five minutes on the hair extensions. Rinse thoroughly in warm water and gently towel blot to remove excess water. For excessively dry hair extensions, use a deep conditioner free of silicone, parabens and sulfates to add much-needed moisture. Follow with a leave-in conditioner before combing the hair extensions.