What's this whitey/yellowy stuff on the underarms of my shirts?

I presume it’s something to do with my deodorant and/or perspiration. What is it? Can it be removed (ordinary washing doesn’t)? Can I prevent it?

This isn’t a new problem, it’s just seemed to be worse lately. I’ve used the same type of underarm roll-on deodorant for years, and I’m not aware that I’m perspiring any more than I used to. It’s got to the point where I’m afraid to wear new shirts for fear of ruining them. Call me Scruffy…

Those are sweat stains. If it’s a white shirt, bleach is likely to help. Otherwise we’ll have to wait for someone to come along who has greater knowledge of fabrics.
As to why you’re experiencing it now and didn’t notice in the past, you got me.

Both the sweat marks, stains, and the smell is caused by bacteria.

Try using an antibacterial soap during your showers.

Try a borax-and-vinegar paste. Let it sit a while and rinse.

If the OP is thinking about what I’m thinking about, it’s more than just sweat stains. I’ve had T-shirts get stiff in the armpits, almost like polyester fibers that have fused. But, I’ve had this happen to T-shirts that are 100% cotton. Also, if the T-shirt is white, the stiff parts a off-white.

This doesn’t come out in the wash and doesn’t have any kind of odor that I can detect. I assume this has something to do with deodorant but have never had anyone confirm or deny it.

lipfuscin

I’ve had the same problem my whole life. Always wear an undershirt and pre-treat before you wash. Once you put clothes in the dryer with stains on them, they become much more difficult to remove.

Uh huh. And where does that article leave GIRLS who have the problem?

Anyway: my experience is that bleach does not work. Cheryl Mendelson says to use a laundry pre-treater. Me, I just relegate white shirts to undershirt-only status when they begin to turn.

My boyfriend has had success treating the stains with a slightly diluted solution of Simple Green before washing. Seems to work best on shirts that haven’t gotten too bad yet. You might need to repeat the process a few times.

Of course YMMV, and I would try the Simple Green on an inconspicuous area first to make sure it doesn’t have any ill effects on the fabric.

I had the same problem all my life. When I stopped using a roll-on deoderant, however, and switched to a spray-on deoderant, the problem stopped. Been doing this for 3 years now…no longer have the yellow stain problem.

Oh, one other thing that I’ve changed: I keep my under-arm hair trimmed (yes, I’m a guy). I assume that because less moisture accumulates down there, less water gets on my t-shirts. It also seems to take longer for my under-arms to emit odors.