ΔE 15.2, loose: different enough that you should pick on purpose. Off-White is a little darker, more muted, warmer than Sickly Skin.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Off-White is a little darker, more muted, warmer than Sickly Skin.
The same difference applies the other way round: Sickly Skin is a little lighter, more saturated, cooler.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Sickly Skin on the colour wheel See Off-White on the colour wheel
All matches: Sickly Skin equivalents · Off-White equivalents