Thank you for the info Cobgoblin. Hopefully this was a one-off event then. I’ve just been down the field to check on him and he made it perfectly clear I am an untrustworthy horse abuser who can just feck offThey usually develop when an injury, which could even be a small puncture, drives some cells from the outer layer of the skin into the deeper layer. As these cells will often contain hair roots, the hairs continue to grow, often with the greasy sebaceous gland secretions.