Yellow marks on white school shirts

[PercyPigs1]

I'm noticing sweat marks on my daughters school shirts. I wash them at 40 synthetics with non bio as she had sensitive skin. Any tips for dealing with them? Thanks

Bio laundry detergent isn't necessarily a skin irritant - it's usually the added fragrance. That said have you tried adding some kind of oxygen bleach to the wash? Hanging out the shirts in bright sunshine should also help reduce the stains.

Also, if your daughter applies antiperspirant at night it gives it time to soak into the skin which should help minimise the staining and it should actually work better as she won't be sweating it off which is what happens when it is applied in the morning.