Hello David, Thank you for asking at HCM. Although both walnut & fish are known as major food allergy causes, your history is not typical of that of a food allergy/reaction. Most important thing, an allergic reaction cannot cause one-sided symptoms, in your case you have blocked right sided nostril. One-sided symptoms usually point to some local cause. Fish is considered a histamine-rich food, however, again, histamine would not cause one-sided nose blockade. One more thing, food allergy usually manifests as rhinitis symptoms within 1-2 hours of consuming food. So by keen observation, you can know that which food may be the cause. Thus, although both walnut & fish are considered highly allergenic, and they can be tasted for allergy also, at present I would suggest you not to worry and if you have significant one-sided nasal obstruction, I would advice you to consult an ENT specialist who will examine the nasal cavity. Hope this will help you. Wish you best of the health. Regards.