Cob Houses Made of Dirt and Straw

These beautiful houses are all made out of dirt, straw and clay. They are fire-proof and very stable. Amazingly, they don't shed dirt all over the place.

The name of the style of construction used to build these houses is called "cob." Wikipedia explains: "Cob is a building material consisting of clay, sand, straw, water, and earth, similar to adobe. Cob is fireproof, resistant to seismic activity, and inexpensive. It can be used to create artistic, sculptural forms and has been revived in recent years by the natural building and sustainability movements... Cob is an ancient building material, that has possibly been used for construction since prehistoric times."

My only question here is whether these structures are hypoallergenic.