A lot of people message me on YouTube and Tumblr asking about dietary restrictions in Korea and to be quite honest, it can be tough.
Not many people in Korea have food allergies like I am used to in the US (peanut allergies, being lactose intolerant, etc) So when non-Koreans come to Korea and start to ask for certain foods to be changed (like, please don't add carrots) because of an allergy, its uncommon so restaurants often aren't sure what to do.
Recently though, there has been a movement to make vegetarianism and veganism more accepted in Korea, a country famous for its meat dishes, and as a result people are learning more about food and different diets!
My friend Sunny is Korean and in her late teens she developed allergies to a ton of different things, including gluten. Because her diet because so restricted, she started cooking for herself. She then discovered a small but hungry group of gluten-free people in Korea who wanted some of the desserts she had been baking for herself.
After gaining more and more popularity, she opened Sunny Bread and now serves everything from cheesecake to tiramisu to pumpkin pie, all vegan and gluten free!
She also knows how hard it is to have an allergy, plus she speaks English really well, so if you go in nand talk to her about what you can and can't eat, I'm sure she'll have suggestions for where to eat in Seoul :)