Help needed - armpit stains

[LittleArithmetics]

All my DH's shirts develop sweat/deodorant stains in the armpits over time. I've had reasonable, although not perfect, success getting them out with Vanish powder and bicarb and stuff, but it's a time consuming job and I'd really like to prevent the stains in future rather than taking retrospective action. I'm wondering, what's the best way of pre-treating shirts before they go in the wash to reduce this problem? Also, could our washing powder be partly to blame - we're using Ecover non bio. Would a bio powder make much difference?

I keep a spray bottle of 50:50 white vinegar and water by the washing machine and spray every armpit before a wash. It helps with the smell and at preventing stains!

As @Whoopsies said, white vinegar sprayed on before washing will deal with sweat. Don't know if it helps prevent build-up of deodorant though.

Thanks, I'll try the vinegar spray. @Whoopsies do you put them straight in the wash after treating them, or leave them for a while for the vinegar to work?

Does anyone think the washing powder is relevant?

You probably need a bio powder but also change the deodorant I find right guard causes staining on clothes and so do some other types. Changing solved the problem for my son.

I think it’s the deodorant more than the sweat that stains, we switched to a more natural ‘salt of the earth’ spray and noticed this doesn’t happen anymore… I did buy a specialist remover type product but it didn’t do that much to existing stains.