Source: Esthetic Association Florida

"Want to steer clear of dry, flaky skin? Grab an orange, a carrot, or a slice of cantaloupe.
These fruits and vegetables are loaded with vitamin A, which helps hydrate the lower layers of the skin. Other good food sources of vitamin A include leafy greens, eggs, and low-fat dairy such as cheese and milk.

Psoriasis
Neotigason capsules contain the active ingredient acitretin, which is a type of medicine known as a retinoid. Retinoids have a structure similar to vitamin A and are involved in the normal growth of skin cells.

Acitretin works by inhibiting the excessive cell growth and keratinization (process by which skin cells become thickened due to the deposition of a protein within them) seen in psoriasis. It therefore reduces the thickening of the skin, plaque formation and scaling.
This form of Vitamin A will stay longer in the subcutaneous layer. Or adipose layer. Using this form of therapy, woman need to prevent pregnancy even two years after undergoing this type of treatment.
The use of this medicine will be supervised by a skin specialist (dermatologist). It is reserved for treating severe skin conditions, such as psoriasis, when other treatments have not been effective.

The natural form of Vitamin A is stored in the liver. Too much Vitamin A can cause baldness and dry flaky skin. Lack of Vitamin A in the body also can cause dry and flaky skin, it even can lead to blindness.

Vitamin B.
B vitamins are water-soluble. Lack of Vitamin B1 can cause Beriberi, edema, heart problems and nerve and brain dysfunctions.

Lack of B2 can cause fistula in the corners of the mouth. Blepharitis, a common eyelid inflammation that is sometimes associated with a bacterial eye infection Seborrheic eczema on the face and around the eye’s.

Vitamin B3 or Niacin.
Most people can make niacin out of tryptophan. Lack of tryptophan can cause pellagra. Pellagra is classically described by "the three D's": diarrhea,dermatitis and dementia. This happens more in area’s where people eat a lot of corn ( USA and Italy) People who have a lack of Vitamin B3 have a high sensitivity to the sunlight. And skin disorders will appear in area’s that are exposed to sunlight, like face, neck and hands.
In elderly vitamin B3 deficiency can cause mental confusion. In children it show as cracked lips and red skin lesions.

Vitamin C:
Vitamin C helps protect skin from the sun. It also helps undo damage done by free radicals, which destroy skin-firming fibers such as collagen and elastin.
Lack of Vitamin C can cause small bleedings around the hair follicules
Excellent sources of vitamin C include red bell peppers, citrus fruits, papaya, kiwi, broccoli, greens, and brussel sprouts."