Yeah antiperspirant causes pit stains.
I`m not very sweaty,
and I use only deodorant,
and I have no pit stains on my shirts.
My roommate is more sweaty,
and he uses quite a bit of antiperspirant,
and he has stains on his t-shirts.
Some of these stains actually get sort of hard and crusty,
and it`s from caked-on antiperspirant.
Most of the color in these stains comes from the aluminum compounds in antiperspirants,
although sweat alone can stain too.
If sweat alone is staining clothing,
the substance responsible is what is called urea,
which is a bodily waste product also found in urine.
The thing is,
both aluminum salts and urea are difficult to remove from clothing.
They both have a tendency to dye the clothing.
Urea is used to help dyes set into clothing.
The aluminum compounds in antiperspirant can create a sort of rust that is almost impossible to remove.
Most stain-removal guides I read say that armpit stains are some of the most difficult to remove,
next to ink.
But you might have some luck.
The best stain-removal guide I know,
found here: http://www.human.cornell.edu/TXA/Outreach/upload/removi...
suggests a multi-step approach to removing antiperspirant stains from clothing.
I`ve sort of condensed the steps for you to make it simpler.
The reason for multiple steps is because the different components of armpit stains--aluminum and sweat and the other things in the antiperspirant require different methods of removal.
Soak the clothing in a bucket overnight with a half-cup of ammonia and a couple tablespoons of detergent.
Then launder as usual.
If you do this soak directly in the washer,
use a full cup of ammonia and your regular detergent amount,
agitate for 5 minutes,
then let soak overnight.
Complete the cycle the next day.
is quite gentle to fabrics.
You can try repeating #1 if you got good results.
The stain guide I referenced recommends moving on to soaking the stained clothes again in vinegar.
Use 1 cup in a bucket,
or 2 cups in the washer,
with detergent as suggested in #1.
and complete wash cycle the next day.
After this soak,
it is suggested to use bleach,
if the clothes can handle it,
to remove the rest of the stains.
Use 1/4 cup in a bucket of water,
or 1/2 cup in the washer,
follow the instructions on the bleach bottle.
Soaking time is much shorter:
Check the clothes every 10 minutes,
and don`t let them soak for more than 30,
or you risk dissolving them.
You probably can`t use a long bleach soak on colored or delicate fabrics.
Drain the bleach solution from the clothes and wash as usual.
Final notes and suggestions:
If you have delicate clothing to treat,
you can do the above steps as a spot-treatment,
rather than soaking the entire garment.
Be sure to test your solutions on a portion of the garment that cannot be seen to make sure it`s safe.
NEVER NEVER mix ammonia,
bleach or vinegar with each other,
or you could get poison gas.
On the other hand,
I`ve found from personal experience that ammonia is a cheap and very effective cleaner that most people overlook nowadays.