You might want to check the labels on your hair smoothing products to make sure there's no glyoxylic acid.

This is because it has been linked to kidney injury with the formation of oxalate kidney stones after it comes in contact with your skin.

This is a great example of how chemicals in many household cleaning and personal care products are assumed safe until proven harmful, when perhaps they should be assumed harmful until proven safe.

Fortunately, in this case, kidneys seem to recover when contact with glyoxylic acid is ceased.

Have a read about it in The New England Journal of Medicine https://www.nejm.org/doi/10.1056/NEJMc2400528