How to Handle Dietary Restrictions at a Wedding

Hosts
Guests

When throwing a party with hundreds of guests, you're going to be dealing with hundreds of palates. While you obviously cannot accomodate every single like and dislike at your celebration, it is nice to be able to provide options for your guests. After all, you don't want to pay for a dish that someone cannot eat because of a food allergy; that leaves you out $100 and them hungry.

If You're Hosting a Wedding:

with a buffet

Put a line on the RSVP card for any food allergies or dietary restrictions (the language used may elicit different responses i.e. "food allergies" doesn't take preference into account and may result in fewer varieties needed.)
See if your caterer can prevent cross-contamination and ensure an allergy-free dish. If so, put one or two on your menu. If not, let the guest know that he or she may want to bring snacks or eat beforehand.
Provide a vegetarian option.
Provide a protein, preferably without dairy.

with a sit-down meal

If there are multiple meal options, list them on the RSVP. The more specific you can be, the better. If you know that an option is nut-free, dairy-free, gluten-free, etc. place that next to the meal option.
Place lines next to the meal options so that guests can check off, initial or number which they'd like.
It is up to you whether or not you want to put a separate line asking for any dietary restrictions.

If You're a Guest With a Dietary Restriction:

If there is a place to note your allergy or restriction do so.
If there is not a place to do so and you aren't sure whether the meals will be okay for you to eat, see if you can contact the caterer. You may be able to do so by contacting the venue, giving them the name of the wedding, and asking for the caterer. If this information isn't available, leave a note on the RSVP.

-Only leave a note if your restriction will prevent you from eating an entire plate of food. If you can pick around something, try not to bother the hosts.
-If you must leave a note, say "Whichever plate is gluten-free" or put a number next to your preferred item and say "if gluten-free; if not, whichever plate is gluten-free."
-If you feel more comfortable contacting the host directly, do so. Ask, do not demand, if any of the plates are okay for you to eat. If not, and the host doesn't offer to customize a plate for you, bring snacks or eat beforehand.