B
buffalo
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Yes, there is an explanation. It is called the “Sudarium” and it has a known provenance from Jerusalem to Oviedo, Spain.
It is a piece of folded linen cloth pinned with a strip of cloth over the face of a body that hung upright while dead, with the face leaning to one side. It has both blood stains and pleural oedema (fluid that would have leaked out of the nose from the lungs after death while the body was upright and again when being moved).
No image is found on the Sudarium, but the blood spots that would have been present on a thorn-wounded head correspond to those on the Shroud of Turn, as does the blood type (AB). (www.shroud.com/guscin.htm) This article goes into more detail about other things found on the Sudarium such as pollen and residue from what is possibly aloes and myrrh.
Author Janice Bennett has just published a book (on my reading list, but not in my grubby little hands) called Sacred Blood, Sacred Image (Ignatius Press) which goes into more detail.
(Her book on the Holy Grail & the recently-found letter of St Lawrence is also on my list of things to read…)