Dear Preston: Do I Need To Warn Guests With Allergies?

Dear Preston:
You once designed a summer event for us and used some of the most fragile and beautiful flowers in your designs. Unfortunately,  several of my guests suffered from terrible allergies and were sneezing their heads off! I was shocked and felt terrible. I wonder if there is a certain protocol I should have followed. Is it my job to warn guests in advance?
Dear Allergic:
This is the first time I have ever received this question and I am glad you asked. I have had many brides and guests who have been allergic to specific flowers and plants (see a behind-the-scenes image of one above), but they have always come prepared. In fact, I once had a bride who was allergic to all flowers and she still insisted in having the ones she loved at her wedding. She spoke with her doctor and took the right medications to make that possible. In my experience, most people assume there will be flowers at weddings and travel with the allergy medications prescribed by their doctor. With this questions in mind, it might not be a bad idea to warn them personally (not in your invitation) and have some non-drowsy allergy medications available at your next event.
What do you think, readers? Do you think hosts need to warn guests about these sorts of things or is it taking things too far?