Yes, crystallized honey is safe to eat.You know honey has crystallized when it looks very thick and very grainy. It also lightens in color compared to when your honey was pourable. Crystallized honey is perfectly good to eat and preferable to many people. Some people prefer it because of its ability to spread easily without dripping.
The tiny little grains of crystallized sugar give your once liquid, amber honey a very fine texture. Think of crystallized honey as a smoother version of rock candy. Instead of the sugar crystals being big and crunchy like in rock candy, the sugar crystals are small and smooth.
Raw honey is more likely to crystallize than a processed honey. This is because very small pieces of the hive will remain in your honey while the beekeeper extracts the honey. It could be small pieces of comb, previously crystallized honey, beeswax, pollen, or propolis that begin the crystallization of your honey. All are edible and healthy bits, but they speed up the crystallization process.
To turn your honey back into its liquid state, it must be heated. You begin to lose some of the health properties of your raw honey when it is heated past 110°. My advice is just to enjoy it the way it is, crystallized or not.
If you want to return your crystallized honey back into a liquid, you will have to heat it up. Microwaving it is the quickest but will also ruin a lot of great qualities your honey has. The best way to warm your honey is slowly in water that is about 110°. A double boiler is the easiest way and most gentle way to heat it back up. If you get it to 160° or above, you are pasteurizing it.
Adam Hickman works in the Cooking Light Test Kitchen and as a beekeeper in Birmingham, founding Foxhound Bee Company in 2014.