Especially in brick masonry, a wall can develop efflorescence. The question "is efflorescence dangerous" comes from the fact that efflorescence looks a lot like mold, and mold spores can be dangerous to people. Also, since efflorescence is caused by water damage, a lot of people wonder if efflorescence is dangerous because they are concerned for the structural integrity of their brick masonry. Both of these concerns are valid and are addressed below.
When water passes through brick masonry, it can crystallize causing a white residue called efflorescence. This efflorescence can be mistaken as mold because it is caused by water damage and can look a lot like some types of mold spores. Since mold spores can cause severe allergic reactions in some people and even breathing problems if the mold is considerable, mold is a huge concern. However, the question "is efflorescence dangerous" is not applicable to this type of situation since efflorescence is not dangerous to people in the way that mold is.
Is Efflorescence Dangerous?
Moving on, the other possible danger of efflorescence, structural integrity, we can answer the question " is efflorescence dangerous" more easily in this situation. Because water damage has to be fairly severe to cause efflorescence, it is safe to say that it can be quite a problem for a masonry structure. And while efflorescence doesn't actually cause spalling like water damage in concrete, it is a sign of weakness in the masonry and should be addressed and corrected.
A hydrophobic sealer that penetrates into the masonry deep enough to prevent the efflorescence is one good way to prevent the water damage that causes efflorescence. However, this type of sealer shouldn't be used in areas where the weather gets cold enough to freeze.
If you already have efflorescence, you can get rid of it by phosphoric acid diluted with water. Follow the instructions on the bottle very carefully to make sure you are mixing it correctly. Use a diluted, mild detergent to neutralize the acid, and then rinse the masonry with water. Also, you will want to be sure to address the source of the water to prevent further damage.
For more information on is efflorescence dangerous