You can plane MDF but, I would advise against it. Yes, it will definitely dull your blades faster than wood. The dust is the main reason I avoid MDF. Here is just one portion of an article about MDF use.
Wear a good mask
There’s one thing you’ll really hate about MDF: the fine, powdery dust that invades your clothes, hangs in the air for hours and clings to every surface like a coat of frost. Cutting MDF is a dusty job, but routing it is even worse.
Whenever possible, I cut and rout MDF outside. When that’s not possible, I drape sheets of plastic over shelving and other hard-to-clean areas in my shop and use a fan to blow dust outside. When installing trim in a room, cover doorways, close air vents and expect to vacuum every surface when you’re done, even the walls. Clean your vacuum filter often—the fine dust plugs filters quickly. And a tight-fitting dust mask is essential.
The entire article can be found here:
https://www.familyhandyman.com/woodworking/woodworking-tips/what-is-mdf-plus-tips-for-using-mdf/God Bless! Spirithorse
