Can i take allegra (fexofenadine) d 24 hour with nyquil cold flu?

Avoid both: There is a small but real risk of respiratory depression (quitting breathing), or cardiac arrthymia due to a delay in the electrical signal that tells the heart to beat.

Allegra (fexofenadine) D : For treating allergies, Allegra (fexofenadine) d has been shown to be effective and safe. There is likely not much to be gained with adding nyquil except getting sleepy and a dry mouth. Try to avoid cough/cold products with multiple ingredients mixed with alcohol.