This has just been noticed on at least 3 different doors. It looks like varnish but doesn't have any smell that I can detect. He's lived there for 2 years this is the first time this has happened.
The last 3 images are 2 different doors to the earlier ones. Whatever it is, seems to avoided the notch in the wood, but you can't really tell because of the lighting in the photos :S
Anyone got any theories?