Looking for some insight as to what could be on our upstairs bathroom walls. In this picture you can see what I'm referring to. The substance builds up on all four walls, usually higher up in the bathroom. I would describe it as orange-ish and slightly tacky/sticky or dry to the touch. Typically after a shower it's easily wiped off the surface, but will come back regularly.
We have a crawl space behind the bathroom, and I've recently noticed the same in a few areas there as well.
Is this mold? Could it be originating from the fan vent, the roof or paint? We've lived in the house for 2 years and it's always been like this.
Thanks for any help you can provide.