I was recently appalled to learn that many shampoos contain formaldehyde-releasing additives. [View all]

This is not a mistake, or contaminant, or by-product -- these compounds are *intended* to release small amounts of formaldehyde over time, to act as preservatives.

https://en.wikipedia.org/wiki/Formaldehyde_releaser#Safety

While they are claimed to release formaldehyde (FA) at levels low enough to be "safe", some people are allergic to FA and develop contact dermatitis from exposure. Check your shampoos and cosmetics for any of these ingredients:

Quaternium-15

DMDM hydantoin

Ureas (imidazolidinyl, or diazolidinyl)

Benzylhemiformal[1][2]

There are currently a couple of class-action lawsuits in process (J&J, Nexxus) over hair loss by shampoo users. Some of the articles found with Google are a little long on the woo, but there are also more balanced ones out there. Here's a sample: https://www.ewg.org/news-insights/news/2021/08/does-dmdm-hydantoin-really-cause-hair-loss-heres-what-you-need-know

If your shampoo actually causes your scalp to itch and hair to fall out, there's definitely something wrong.