you say the slab is missing, is this just around plumbing or other items coming from under the slab? around here slab houses usually hav ethe plumbing and some electrical conduits run before the slab is poured. then they box in around the plumbing and pour the slab, leaving a small "hole" in the slab. if you look under the tubs in my house, there is slot about 2ftX1.5ft of missing slab where the water pipes and drain line come thru. no mold issues there.

are you sure you have not had leaks?

if you want to block moisture from coming in at those points, maybe fill each hole with spray foam. then treat and kill the current mold. if it is bad enough, or certain types of mold, your only recourse is removal of the affected areas. some types cannot be removed, as they easily spread elsewhere and the entire house must be abandoned.

i read about a couple that had this happen to their brand new multimillion dollar home. the contractor pierced a water line, and a slow drip caused so bad of mold the house was condemned and for health reason they could not even take the clothes on their back with them when they were forced out. hope yours is not that bad!

Thank you for your reply.

Yes, the slab is missing 1) under the kitchen sink, 2) under the wall between the kitchen and bathroom where some pipes go into the ground and 3) where the shower drain goes into the ground (in another closet). Under the kitchen sink is an old well head, it shows you they didn't have city water when the house was built, and I found the old septic tank too! (It's empty.) We now have city water and sewer.

House was built in 1954. Yes I did have the original drain pipe going from the kitchen sink to the main sewer rust through. Water collected under the kitchen sink. I had the pipe replaced (half of the bathroom slab had to be demolished then replaced), so that problem is fixed.

No, mold is not that bad, but when I look under the sink I can see the studs and black stuff all over them, which I assume is mold. The other part is I am very allergic to mold and my asthma is acting up since I have been in this house. Before I moved in I didn't need medicine. Now since I moved into this house I take medicine every day, except in the summer months.

Asthma problems only during cool months point to a probable mold problem.

Any suggestions for a spray that will keep killing mold once it is sprayed on?

I am allergic to mold too - every mold I've been tested for.

I have mold behind the paneling in my basement, but nothing that's out of control. I use a dehumidifier, which seems to help. As far as treating the mold, try a product called "Mold Avenger" - recommended by a reputable paint store that I go to on the other side of town. I was told this will help reduce the mold greatly, but will not rid it entirely or forever, but it is not harmful to your health and is effective for up to a year. You can help to prevent regrowth by removing the elements that are creating the mold. If it's moisture, reduce the humidity in your home with an air conditioner or dehumidifier or a combination of the two.

Good luck!

You need to open all the areas that you see mold on. Spraying only the exposed mold is useless. Dumping chlorine into walls is dangerous and not effective. Open the areas and have them treated professionally. Fill in all the missing areas with concrete over a vapor barrier.
Ron