Your friends, family, and colleagues probably won't understand why, all of a sudden, you're not eating the same things they are. It helps to develop a brief explanation that explains your health issue in a simple way. For example, I typically say, "It turns out that I have Celiac Disease, which is an autoimmune response to the gluten found in wheat, barley, and rye; since those ingredients are found nearly everywhere, it's safest for me to eat things I know are gluten-free."
This brings us to the next tough social situation: a party or social gathering at someone's home.
A potluck is actually a great environment for staying gluten-free. You can bring a dish to share that you'll enjoy eating, portion some out for yourself before the dish is contaminated by shared utensils, and no one will even notice what you're eating. I often volunteer to bring mashed potatoes, risotto, rice dishes, or plain tortilla/potato chips with a gluten-free dip. However, the other party guests may dip bread into the dip, use the serving utensil from a nearby dish, or otherwise contaminate the food. This is why I suggest eating only what you've brought, or taking the first serving from a gluten-free food.
Your well-meaning friends and family may try to cook gluten-free items for you. Since they likely are uneducated about cross-contamination in the kitchen, I suggest heading them off from the start by explaining that it's taken you quite some time to figure out how to prevent cross-contamination, and it's best for you to prepare your own food. If someone really wants to try to feed you, gratefully accept products that are labeled as gluten-free, or offer to help them cook. It's extremely difficult to say to someone that you won't eat something prepared specifically for you; however, you need to remain in control of everything you eat. If someone offered you a salad, you might want to think about the following: are they using a wood cutting board which might house remnants of gluten? Did someone use their countertop to slice bread and not sufficiently clean it? Are their baking ingredients uncontaminated? Did they check with the manufacturer for every ingredient they used, or use shared utensils that aren't easily cleaned (like a mixer, sifter, strainer, etc)? In all likelihood, those thoughtfully prepared meals simply aren't safe for you.
One great way to control the food at a social event is to host it yourself. I love to host holiday meals and family get-togethers. When someone asks what they can bring, I give them a specific brand or product which they can contribute. If there are favorite gluten-containing recipes, I suggest that someone bring that recipe for the rest of the group. This way, I haven't contaminated my kitchen, and everyone gets to enjoy food they love. I don't typically tell non-Celiac guests which items are gluten-free, since some may have preconceived notions about yucky gluten-free foods. Most typical holiday foods can be made gluten free. You can roast any meat and cook the stuffing separately, or use gluten-free stuffing. Vegetables, potatoes, gravy, and more can be made gluten-free with little effort. For desserts, I suggest you plan your favorite gluten-free dessert, and let others bring gluten-containing items. For example, I'll make a gluten-free apple pie using Whole Foods' gluten-free crust, and no one will be the wiser. The same goes for cheesecake using ground almonds for crust. This way, you'll know to avoid items brought by your guests, and still be able to offer a delicious gourmet dessert.
By helping your friends and family understand that eating gluten-free is essential to your health, you will be more in control of your diet and gain social support from those close to you. The people around you care about you and want to see you healthy, so by persuading them that you are the best judge of what is gluten-free, you can enlist their support in planning and preparing for food-oriented events. Anyone who offers to cook something gluten-free is trying to support you, so it's a great idea to thank them for the thought, explain that you're more comfortable preparing meals yourself, and offering other ways for them to help you. By helping your friends and family understand that eating gluten-free is essential to your health, you will be more in control of your diet and gain social support from those close to you.