Efflorescence is the term for lime-salts leaching from concrete and crystallizing on the surface of the concrete. This can occur on floors, masonry walls, foundations and even soil. Efflorescence is not the problem. The root cause is moisture, and this will continue to be a problem until you address the source of that moisture. Most likely, in your case, the source is irrigation in summer and poor drainage in winter. If you have a home built on a slab, the moisture could be affecting the entire structure.

In the garage, this is not a health problem, but as you know, objects stored on the floor need ventilation under them to prevent moisture damage or mold. The same is true of any structural wood (sill plates) that are in contact with the slab. In the home, this could be a health problem if carpeting or padding is becoming moldy as a result of moisture intrusion. The best way to check is to have a section of carpet lifted to inspect the backing.

The solution is a combination of perimeter drains and/or proper grading, and avoiding excess irrigation near the foundation (a carefully controlled drip system that never causes ponding would be better than shrub sprayers).