Over time I get a hard buildup of something in the underarm regions of my white T-shirts. Is there a reaction with gel type antiperspirants and bleach that could cause this?
This is a great question – underarm stains are a big problem to treat because they are highly variable. Each person’s unique body chemistry combined with his/her choice of deodorant creates pretty individualized stains. What works to remove one person’s stains doesn’t always work for another so hopefully this advice will be helpful to you.
The crusty build up you describe is what happens when a person’s deodorant/antiperspirant mixes with body soil and sweat, and transfers onto the shirt. That it doesn’t come off with a regular wash cycle is likely due to several factors, such as how much deodorant is applied, the brand of deodorant, the brand of detergent, and the wash temperature (hotter is better), to name a few. In your case, pre-treating the armpits on the shirts each time they are washed should help you avoid the build-up from happening. Two effective pre-treating methods to try are:
Unless you have an obvious stain you were trying to remove, you can tumble dry the shirts with the rest of your white load; otherwise, let them air dry.
For the stained shirts that you already have, try restoring them using a recommendation often provided in clothes washer user’s guides. Here’s a little more detail on how to do it:
Apply a mixture of 1:1:1 parts baking soda, hydrogen peroxide, and water directly to the stain. Sometimes this is referred to as a paste, but it is actually quite watery, so be sure to mix it up enough so you can saturate the stains.
Also, you asked if the antiperspirant’s gel formulation is potentially a problem. That depends – it may be that with a gel it’s easier to apply more, making it easier for any excess to transfer to clothes. If you have yellowing in addition to the buildup, then check the ingredient list for an aluminum active (metals can interact with bleach and cause yellowing), and if necessary, consider switching deodorant brands.