It is paint. Most new construction around here is treated with that type of primer in all bathrooms. It's just another added layer of protection due to houses being built so tight today.
Ordinary mold from excess moisture does not make every one ill !! I lived with swamp coolers as a kid and we were all pretty darn healthy !! Plain old household bleach is molds worst enemy !! Use it every time you clean !!
Mart, yes I have wondered about that. We have had a perennial mold problem in our upstairs bath... it is on the rehab list but other projects are ahead of it. I just keep chasing it with bleach every 6-8 months & no one is sick in our household. I do think though that some people do have a serious allergy to molds.
We had a swamp cooler when I was growing up....north Texas summer heat and humidity with damp water being spewed into the house. We had a mildew problem which looks very similar to mold but cleans up easily. Mildew lives on the surface of moist areas and can be cleaned up with standard cleaning products. There are several different species of Stachybotrys Mold, some are more harmful to humans than others that is why it needs to be tested by pros and cleaned out whether it is harmful or not. It's not going completely away as long as there are bits of it living in moist areas behind walls or inside the wall board itself.
Black mold can be fatal to our health and home. Remove mold as soon as possible. I suggest you to use professional mold cleansers and bleach + water solution to scrub the moldy surface. You can also seek help from professional handyman.
Here is how I have dealt with a similar problem with success. Spray straight bleach on the mold to keep it from being air borne. You should see it disappear quickly unless it is deep in the wall. Protect yourself from the mold spores and the bleach fumes (also bad for you) with a mask. Ventilate the room as you do it with the outside air (don’t put the spores and vapor in the rest of your abode). I have used this method for years with great results. Unfortunately you obviously have a water issue. This isn’t just from plants in the room. Roof leaking, water coming in from upstairs windows or pipes, not having gutters properly installed are just a few of the culprits. If this is an unheated room that might also contribute to the problem. The area needs to be dried once you have bleached the area. A small fan and heat in the room can aid the process. If the mold returns repeat the bleach. Then don’t be afraid to pick at the wall removing a small area to see if the water damage is more extensive (like rotten wood and more mold under the plaster). You can watch YouTube videos for patching. It really isn’t hard or expensive if nothing else is going on. If you have rot and more mold in the ceiling and wall you will know to start saving for repairs. Good luck
