The only place that you can be sure that the pizza dough is vegan is in Italy. This is something that I've learned in all these years of being vegan. In Brazil they might use eggs, so I'm used to always ask about the dough before even considering asking about vegetarian options or to have a pizza without cheese. In Dublin is not different, some pizzas places have eggs or milk in their dough and it's not that easy to find a vegan option in the end of the day. Back in February 2010 I was checking the Domino's Pizza website to try to find some information about their pizza dough. If you go to Food Guide Introduction, you'll find the topic "Pizzas Bases and Toppings - Ingredients and Allergies" and it's a PDF with all the ingredients.
As you can see, "milk" is marked with the "x" for all bases. If you take a look in the Ingredients column you might think there's no milk there in the firs item, "Regular Crust Dough". It's not that obvious (mainly if English is not your mother tongue of if you became vegan recently). But "whey powder" is a milk derivative product. It may sounds silly for a lot of people, but I'm sure that a lot of other people aren't aware of this information.
To make things even clearer, I wrote an email to Domino's and I got two different answers. If I had stopped with the first answer, I would probably ended up buying a pizza from Domino's:
Answer 1: "Hi Glauce, There is no milk or egg in our regular dough base. The milk would predominantly be contained in the cheese. Hope this help."
But I wrote a second email saying that I'm vegan and that the word "milk" was marked in their ingredients PDF.
Answer 2: "Hi Glauce, The base does appear to contain a stabilser which contains whey powder. I was not aware of this as it does not state it on the product in store. Whey is a derivative of milk and is used in a huge amount of food ingredients and flavourings. There is no actual milk added to make the dough. I hope that this helps you further."
It's important to know the questions you're making when you're eating out or wondering to ask for delivery. Sometimes people just answer to our most usual question: "Is there any eggs or milk in this product?" or even "This product has anything with animal origin?" A lot of people don't know all the answers and most of the times they are too lazy to check. Make sure you're asking all the questions and that you received very clear answers.
I don't know if Domino's has the same ingredients for their products in other countries, if you know about it (or even about any other pizzerias that people usually think that offer vegan pizzas but this is not true), please feel free to share with us!