Fire resistant door cores, door skins, and doors including the same

A door core comprising:

• a door core body having a first major surface and a second major surface opposite to the first major surface,
• the first major surface comprising one or more first inner panels, one or more first recesses contiguous with and surrounding entireties of one or more first perimeters of the one or more first inner panels, and a first main body contiguous with and surrounding entireties of one or more first perimeters of the one or more first recesses, wherein the one or more first recesses are recessed from the one or more first inner panels and the first main body, and wherein the one or more first recesses continuously and integrally connect the one or more first inner panels to the first main body so that the one or more first inner panels, the one or more first recesses, and the first main body collectively constitute a unitary piece;
• and
• the second major surface comprising one or more second inner panels, one or more second recesses contiguous with and surrounding entireties of one or more second perimeters the one or more second inner panels, and a second main body contiguous with and surrounding entireties of one or more second perimeters of the one or more second recesses, wherein the one or more second recesses are recessed from the one or more second inner panels and the second main body, and wherein the one or more second recesses continuously and integrally connect the one or more second inner panels to the second main body;
• and
• fire retardant material applied to the one or more first recesses and the one or more second recesses and to neither of a remainder of the first major surface excluding the one or more first recesses nor a remainder of the second major surface excluding the one or more second recesses.