Hi Mumz :) Dry skin is very much a sign of fatty acid metaolisim being interfered with!
Niacin is marked for aiding with absorbing oils in the intestines, killing off candida (anti fungi action), etc, and it's part of the ATP cofactors (500 mg inositol hexanicotinate, 100mg riboflavin) that are reccommended with Iodine use.
The other cofactors are discussed in VWT teams's gdoc summary :) (selenomethionine, magnesium, boron, lithium, Vit C, celtic Sea Salt , and B's)