These days with people so ready to sue anyone for anything, it is wise to put what something is made out of. But, more importantly for those that are allergic should have an idea if something will cause them harm.
At bake sales or anytime I make something homemade to eat, I always give out the recipe, so that the receiver can see at a glance if something will cause them a problem. I am allergic to cilantro and I am always amazed how many things people make that have cilantro in the recipe, much to my chagrin.