Is doxylamine safe to take if allergic to ondansetron chlorpromazine and phenothiazines?

Probably: Doxylamine is an antihistamine. All of these drugs have side effects , so i would review this with the physician prescribing it, you can also likely go over it with your pharmacist. My guess is some of the problems you've had with these meds, if not all, are side effects, not allergy. They may be dose related. You might try this at a low dose at first . See an allergist.