I was approached recently by the creators of a website called Allergy Chef. It is the first free online restaurant reservation network for people with food allergies and intolerances in Barcelona and all of Catalunya. They are working in alliance with the medical society SCAIC, Catalan Society of Allergy and Clinical Immunology, to train and inform restaurants how to cater to the needs of clients like us. All chefs in the restaurants listed on their site are actually trained by the organization, and so far there are 36 listed in Barcelona, with more to come. On their site you are able to peruse the menus of each eatery and each item is labeled with a symbol that signifies it as gluten-free, lactose free, or egg free. You are also able to send special requests to the chef, enabling them to make a special menu just for you and adapted to your specific needs.
The website is straight forward and user friendly. Simply insert your location or the name of a restaurant you already know about, and its listing will appear. You can see the restaurant’s menu, location information, as well as customer reviews. There is a blue reservation button which when clicked, prompts you to list all of your allergy needs, party size, and time of arrival. The website does list the phone number of the restaurant, but rather than call and reserve your table, they kindly ask you to do it through the site. The only way that they can keep this service going is through user use, and we can all agree that it is very handy!

We have made our first reservation on https://www.allergychef.es/en/ for this evening. We will let you know how it goes!
Update:
We used the site on Thursday evening to much success! It was so easy, and a relief to have a reservation, as we showed up and actually got a table while other people were refused. I highly recommend this site for your future reservation needs. It costs you nothing, and helps the website creators train more restaurants and chefs to be more sensitive to our needs.