There's a slight discoloration around one of the bathroom lights (can) in our Master bath. It forms a halo about 3 inches out from can, meaning that the darkest part is NOT next
To the rim of the can. My husband removed can. Insulation is dry. No signs of moisture. Drywall is dry. This can is located above the toilet, fairly close to the exhaust fan, and a couple feet from an exterior wall. The other can, located above the bathtub same distance from exterior wall, has no stain.

House/roof is 14 years old. No signs of moisture on plywood roof above this area, although we just looked at plywood from a distance.

Every article says not to treat the stain until you know why it is there. There's a lot of humidity in this bathroom from showers, etc. Is this a condensation problem? But if so, why didn't the other can develop the halo? Can I safely cover it over and not worry about it?

Help! Please! I am a repair dufus.

The most popular cause would be moisture, but sounds like you have done a good job ruling that out.

If moisture is not the cause, and without actually inspecting ourselves, then the cause can be anyone's guess. Heat from the fixture due to too large lamp in the fixture, perhaps oil from the fixture housing, sometimes the housing has a small amount of oily residue left from manufacturing process that may be reacting with the drywall or paint.

Or the inherent condensation in the room reacting to the paint or heat from fixture.

I am really grasping to give some ideas. Any chance some good photos can be provided to help us see what you see?

IF this is a water stain, the most likely source is from the roof boot around the sewer vent pipe. Sounds like you have a very small leak, just enough to stain but not damage the drywall ceiling. Sounds like the water may be running down the outside of the pipe until it hits the ceiling, then over to the light. Why does it show up around the light? Because that was probably where some patching of the drywall was done.

You will have to get over to this area and look up toward the roof for daylight. Even that may not tell you where the leak is. Other way is to have someone get up on the roof with a hose and spray water while you watch for a leak. Have them spray the water up into the air so that it comes down just like rain. Start at the eve and work up the roof.

Hey, you guys are great! I just love that experts are willing to share their expertise. TKR, I took a photo, but don't know how to upload it here
(great album cover, by the way.) You have convinced my husband to do additional exploratory surgery. Go into the attic. Remove the blown in insulation in this area. Spray the roof. Really do the gritty work of finding the problem.

Logically speaking, I just couldn't accept that this one light can could have a problem different from the other one, or different from the light that's located right inside the shower stall. There's got to be some subtle leak. Thank you both so much!

P.S. HKS - our families lived in Alexandria, VA. Not downtown, but the suburbanish parts. My husband and I went to Jefferson High School, and my
Sisters to Woodson. The traffic in that area is a bit too hairy for me nowadays, but it was a great place to grow up.

Um, now I see an "insert image."... Hmmmm it wants a URL, and the picture is on my desktop. http://slackermom1.shutterfly.com/

Try again! http://slackermom1.shutterfly.com

http://slackermom1.shutterfly.com/27

Well done.

To upload images using AMHD use the advanced and click on the paper clip.

That sure looks like moisture to me.

Based only on your cursory inspection that there was no apparent moisture source above, try this for an explanation.

You made reference to shower moisture, and a fan. Do you have teenagers?

Is is possible that someone did not use the fan when showering a long time, or repeatedly?

That recess fixture could be acting as a chimney due to positive air flow up through the fixture, and the moisture condensed on the metal housing. His would only show as in the photo, and there may not be a roof leak, or any other cause or reason above.

Let's see if I can upload this!

I think tkrussell is probably right. You won't see this around the light with the fan because the fan is pulling the moist air and carrying it away. It may also be a "vapor" light. You can purchase a vapor resistant can light. As long as it is installed correctly this won't happen because the device itself is sealed against vapor infiltration.

Thank you both for this info! Still have not convinced hubby to actually enter the attic but am hoping he'll do it soon. There's no floor - needs boards put down, so I can't peek myself. If we find nothing, we plan to install a vapor resistant can.