What is unique about Allepo pepper flakes? Would red pepper flakes work as a substitute?

Suzanne M. is absolutely right, but do try Aleppo pepper sometime. It is medium hot, less hot than your typical red pepper flakes and it is enormously flavorful. The peppers add a lot more than heat.

You can buy Aleppo at lots of online sources, just google it to get started.

You can definitely use red pepper flakes! Just careful to add gradually and taste as you go along. I specified Aleppo pepper because that’s what I usually use, and it’s more consistent in its level of heat. That way I could be more sure of the heat level I was suggesting. Red pepper flakes can vary a lot in their intensity depending on brand, age or harvest. Also, I like the lightly fruity, smoky flavor Aleppo pepper brings. But it will still be good with red pepper flakes, or without any peppers at all, if you don’t care for capsaicin.