What're some good herbal remedies and supplements for allergic rhinitis?

None that work: There are excellent medicines available over the counter - cetirizine, desloratadine, loratadine, fexofenadine are all second generation, non-sedating and long acting. Chlorpheniramine is an old and dirt cheap but very effective short acting 1st gen. Diphenhydramine is dirt cheap, very effective but highly sedating and best used at bedtime.

None proven: If the anti-histamines mentioned by my colleague do not control you symptoms, you probably will need prescription medicine and/or desensitization therapy (allergy shots). You would have to see an allertgist.