I copied this from another forum:

"This isn't as bad as you might think. Dirtys sock syndrome is bacteria growing, usuallly in the coil and pan area. The solution is for your service company to do a thorough cleaning of the indoor coil, pan and drain, using a good, stiff mix of coil cleaner and disinfectant, like Lysol. The entire area must be kept WET for at least 10-minutes and then be thoroughly rinsed to flush away the bacteria."

I replied to your original post from 8/1.

Good luck.

I own an HVAC business and I am a certified indoor air quality specialist. What would solve this problem permanently (after cleaning the coils as garyg said) is to install an ultraviolet C lamp just above your evaporator coil. You can do it yourself very easily. The things are readily available on the internet (Carrier/Bryant and Aprilaire) for about $250.00 or you can have a contractor do it for about $500.00 (systems up to 3 tons) Add about 50% to this figure for a 4 or 5 ton unit which should have a double lamp system.

There are several schools of thought about what these lights will and will not do. Distilled to simplest terms--they won't kill germs or mold "on the fly" flowing through the air stream of your hvac system with any precision. They will kill mold and bacteria on your cooling coil, keep your drain pan clean and improve the heat transfer ability of your coil by keeping it free of the nasty black junk that always seems to grow on coils that don't have a uv lamp. This should eliminate any mold smell originating from your cooling coil and prevent subsequent "seeding" of such organisms to distant parts of your system. It WILL NOT fix problems with existing mold in your ductwork past the area the lamp is installed. Your ductwork should be thoroughly cleaned to fix this (and make sure it is not unconnected somewhere which could cause condensation and mold). Hope this helps, Ken

Maybe it is because where I live there are not a lot of humid days. (this year might be an exception but for the last few days we have had 70's and dry weather). The way kool dude sounds, one would think that all ducts are loaded with black moldy junk. I haven't seen that a lot.

What I have seen is coils that are not draining or get plugged drain lines. If the air speed is too high, moisture will be blown up into the airstream and not be allowed to drain down the coil into the pan. Sometimes a coil tilts back away from the drain hole and water remains in the condensate pan. This can cause coils to collect mold also. I'm not a big fan of UV lights but whatever float your boat I guess.

After 13 years of discomfort each summer and thousands spent!!! Thinking I had Dirty sock syndrome or a dirty coil
Great news, the plumber found the source of stink (sewer gas) entering my house via positive pressure.
Plumber did smoke test on sewer line today, be for any work was started. It revealed that indeed the sewer gas was not making it past condensation p-trap, but was coming from a uncapped T in the vent stack that was intended to be used to run A/C condensation line when house was built and a unit installed 30 years ago. That said stink is no more!
"So sad, but so true "