[Solved] White Coating Appearing on Painted Wall After 2 Years: Health Risk or Aesthetic Issue?

Good morning.
Inside the room, a white coating appeared on a wall painted with paint in various places on the wall. What could it be. Is it dangerous to health or does it just look bad aesthetically? Will such efflorescence appear when repainting the wall on a new surface? The wall was painted over 2 years ago. Bloom now.

What is the wall made of, more about the building, what kind of paint, what is the purpose of the room and is it heated? Are there any installations inside the wall? What`s on the other side of the wall? Possibility of flooding? How is the room ventilated? Maybe you can take a photo of this raid?

I tried to take a photo, but the light reflects poorly and you can`t see well. It looks as if someone was playing with chalk and then carelessly wiped the spot on the wall. There are many such wall cakes in various places. Mostly on the wall with a window. The child`s room is heated. I don`t know what group the paint is from, but it was bought at Leroy Merlin from their brand`s products.

A dozen or so years ago, when I finished building walls made of the so-called max, i.e. the popular hollow brick.
I also noticed such a coating after some time. The coating appeared after about two years, the walls were "bare" and not plastered during that time, I won`t even mention painting.
The tarnish spots were irregular, the only idea that came to my mind was that the tarnish was caused by chemicals added to the mortar to improve its properties (experts will probably know what I mean).
After plastering without special cleaning and subsequent painting of the walls, the tarnish cannot be seen.

The building is 60 years old. It was insulated 17 years ago. Nothing happened at that time, so it`s not a problem with the external walls and plasters, but it seems to be a problem from the inside. Most likely from the paint. But because I don`t know, I`m looking for answers here.

Not so long ago, the windows were replaced with plastic ones.

The windows were replaced with plastic ones 17 years ago, but they were replaced again 2 years ago. The same situation happened with my friends, but in a block of flats, in a hall with no windows.

The windows may be too tight and there is no natural ventilation. The windows have a micro-ventilation function / handle diagonally and it should calm down.
It wouldn`t hurt to check the ventilation grilles, especially in the kitchen.

So the problem is with ventilation and not looking for the problem in what`s on the wall? The window is open most of the day and open in the evening for an hour before going to bed. The only time I don`t do this is when it`s raining heavily. This coating did not appear suddenly, it has been happening for some time and now it is very visible when there is more of it. The strange thing is that it is dry, like chalk. If it were damp, it wouldn`t look like this

In the meantime, I wiped the entire wall with a wet cloth with Ludwik. I want to see if something starts to appear and if it will be in the same places.

I also have the same problem.
A year after painting, I began to be "attacked" by a strange white coating/sediment on the walls (even those made of plaster).
It can be wiped off and comes back after about a month.
I add a photo in the attachment.

Can anyone give me some advice?
Regards

Welcome back.
It`s still the same for me, maybe a little weaker than before, but I wipe it off every 2 months.

@Malkoni

Are these efflorescences from the putty under the paint due to moisture?

This is some kind of fungus-mould. An identical situation occurred in one of my friends` rooms, where their son had an aquarium. The room is quite small, the aquarium is large (around 150-200 liters). It didn`t seem like there was any evaporation on the entire surface because of the lighting from above, etc., but it was enough to keep the humidity too high despite the ventilation and relatively high temperature in the room. Various chemicals and washing the walls were only temporary methods. The problem ended after the aquarium was closed down

I don’t have an aquarium,
The room is quite small,
I was just wondering if it was some kind of mold or fungus, but I couldn’t find a similar case even in Google.
Insofar as there are such efflorescences on the wall visible in the photo, I can understand it because it is a wall from the "manor" side, but I am surprised that these efflorescences appear on the plaster wall, which is an internal wall separating the room from the room and is not in contact with any sides with the yard.

I will buy a moisture absorber and check after some time how it will look like.
When everything goes away, we will know that it was caused by excess moisture and I will share the information.
Regards

The dehumidifier didn`t help me

no solution