How long are egg-free dressings like Just Mayo okay to eat after sell by date?
I couldn't find a previous answer specific to sell by dates and condiments.  Most condiments, mayo with egg included, are made safe by creating an inhospitable environment for bacterial growth.  The addition of acids (i.e, vinegar, lemon) or other "preservatives" accomplishes this.  Sell by dates are usually an indicator of quality, not safety.  Items such as this are safe for a very long time after the expatriation, especially if unopened, though the quality (taste and consistency) degrades. Once opened, you have the opportunity to introduce bacteria and spores to the contents.  Again, bacterial growth will be inhibited by the product itself.  The most likely problem would be mold growth.  If this occurs, discard.