Can you get pregnancy rhinitis 18 hours after conception? or how soon can it start? can it be five days after conception?

That's a bit: soon but certainly possible.... Time will "tell" Meantime avoid medications if you think you are pregnant without checking them out with your OB-GYN There are "NATURAL" methods of dealing with this pesky medical problem! see (HEALTHLINE NEWSLETTER) Hope this is helpful Dr Z

Pregnancy: Pregnant women can acquire rhinitis the usual way, from rhinoviruses, so at first blush, I don't think you can tell that the rhinitis is due to pregnancy and not allergy or virus. Rhinitis would NOT be a good way to ascertain whether or not you are pregnant.