Is it safe to mix borax with peroxide bleach?

Don’t do it. The borax should be enough, and if you add a cup or two of white vinegar to the rinse cycle, that should take out any residues left over.

I used to wash cloth diapers in borax and baking soda, so I can vouch for its power.

I did a cursory look around on the internet. Both chemicals appear to be oxidizers, and mixing them shouldn’t have any negative effects. In fact one of the supposed products made when mixing water with borax is H2O2 (hydrogen peroxide).

That said, most cleaning chemicals actually reduce one another’s power when used in tandem. And one strong oxidizer is rough enough on a person, let alone two.

Try washing them again with hot water and a mild liquid soap and then leaving them outside in the sun for a day or so.

Do not do that. ))

If you mix sodium borate (borax) with hydrogen peroxide you get sodium perborate which, according to Wikipedia, is one of the active ingredients in most laundry detergents (its also used for bleaching root canal treated teeth from the inside by inserting the stuff into the tooth and leaving for an extended period of time). If you have washed the items with laundry detergent then you have probably already washed them in the product of mixing the two together anyway (not entirely sure that sentence works).

Time for a new set of towels.

Nah. It’s just a little mildew. Honestly, the vinegar alone should have fixed it. I can’t tell you how many times I’ve done that.

Hang in the sunshine after a white vinegar rinse.

I regularly use vinegar and detergent for my towels – @Seek_Kolinahr and @Tropical_Willie are correct.