Re: What is the most common chemical agent in household cleansers.

The most common ingredient in household chemicals is water.  Beyond that is 
mostly depends on the product.

1.  Shampoo/handsoaps: sodium lauryl sulfate
2.  Liquid Dishsoap: linear alkyl benzene sulfonate
3.  Powdered autodish wash: sodium tripolyphosphate, sodium carbonate, 
nonionic surfactants.
4.  Surface cleaners: linear alcohol ethoxylates, glycol ethers
5.  Glass cleaner: isopropyl alcohol, anionic surfactants, glycol ethers
6.  Powdered laundry detergent: sodium sulfate, anionic and nonionic 
surfactants, bleaching agents, whitening agents, antiredeposition agents.

Also included in most detergents are:
chelating agents (EDTA), builders (STPP, sodium carbonate),
pH adjusting agents (sodium hydroxide, phosphoric acid, sulfuric acid)

But without a doubt the most common chemical found in cleaning products is 
good old fashioned H2O.