I am well aware that certain excesses, ratios, or forms of vitamins or
minerals are associated with dry skin, but I have yet to narrow it
down to a specific culprit.

Perhaps someone else can relate to this.  The dryness typically
occurred on the inner part of the eyebrow area of the eyebrows,
especially the right one.  A worsening of the dryness occur every week
or so as other additional dryness would develop in a few spots around
the mustache area.  A few days off the multivitamin--be it either Twin
Labs Daily One w/o Iron or Swanson's Century Formula w/o Iron--has
completely cleared up the problem.

I am a 39 year-old white male.  My diet is mostly whole grains and
vegetables, a little fatty fish every day such as canned jack
mackerel, and some pumpkin and sesame seeds.  The diet (w/o the multi)
meets most of the RDAs, with the notable exception of B5, which seems
to be relatively challenging to meet regularly w/o animal products.

Manganese and selenium RDAs are easily met, typically over 400% and
200%, respectively.  Manganese, in particular, has caught my eye,
since the multivitamins already well exceed the RDA on this, with 5mg
of manganese.  IMO, this is not particularly good.  E.g., from
http://www.online-vitamins-guide.com/minerals/manganese.htm:

Dosage

  Taking 4 mg or less of manganese supplements a day is unlikely to cause
  any harm. For older people, taking 0.5 mg or less of manganese
  supplements a day is unlikely to cause any harm. This is a lower amount
  because older people may be more sensitive to manganese.

While I am not ready to throw out the multis, I am considering taking
them much less frequently, perhaps taking them every other day or
during travel.  In the long run, I might take more specific nutrients
that might be less likely to be met on the diet and with a high upper
safe limit, such as B5.

Any comments are appreciated.  Thanks.