The Earth's Crust is like the skin of an apple. It is very thin in comparison to the other three layers. The crust is only about 3-5 miles (8 kilometers) thick under the oceans(oceanic crust) and about 25 miles (32 kilometers) thick under the continents (continental crust).
The problem behind your itchy skin might be insufficient vitamin intake. There are a number of vitamins that promote the hydration and healthiness of your skin. A shortage in these could trigger itchiness, dry skin and other skin conditions. Alternatively, an overdose of such vitamins might also lead to itchy skin.
A deficiency of Vitamin A can lead you to have side effects including dry skin, dry hair, blindness at nighttime, and an increase in digestive infections. A large excess of Vitamin A can lead to dry skin (just as in a deficiency), hair loss, pain in the abdominals, headaches, and drowsiness.