What is the best skincare for extremely dry skin?

Healthy skin. Avoid things that make you break out, soaps & wetness. Wash your hands only when necessary. Wear gloves when needed. Wear clothes made of cotton. Bathe only with a small amount of mild unscented soap, such as dove. Keep the water temperature cool or warm, not hot! use the medicine your doctor gave you. Use a plain moisturizer daily. Avoid scratching or rubbing the itchy area. Manage stress.
Create healthy skin. I don't necessarily believe in moisturizers for moisturizing sake. Of course if your skin is dry because of damage, then there are many products that can protect your skin. However, the real answer is to create healthy skin by healing the damage done. That means getting your skin to moisturize itself. There is one system that can offer that. Find a plastic surgeon or dermatologist that understands.
Dry skin care. Ceramides. Ceramides help the skin hold water and soothe dry skin. Synthetic ceramides may mimic the natural substances in the outermost layer of skin that help keep moisture in.Dimethicone and glycerin. These draw water to the skin and retain it there.Hyaluronic acid. Like ceramides, hyaluronic acid helps skin hold water.Lanolin, mineral oil, and petroleum jelly. These keep water in the skin.