i think you should ask NSC.
and in the end, other than the NSC specialist making it compulsory
for you to get an excuse, you do have a choice whether to get such
an excuse or not.
of course i am not telling you to forsake your complexion for the
sake of applying camo cream. if it is genuinely serious, then ask
for an excuse, and let NSC decide if the condition renders it
necessary.