Formaldehyde

Mostly found in soaps but also an ingredient in some pet shampoos, you can end up using this around your pet without even knowing you did it. You may have also heard of this chemical, as it is used in a lot of products, from food preservatives to household products all the way to resin, plywood, and fertilizer.

While it is so widespread, formaldehyde is also highly toxic and flammable.

For both humans and pets alike, this ingredient can cause harmful side effects, as its least problematic side effects include nose, throat, and eye inflammation.

In pets, it is a known carcinogen, and it can lead to your pet developing asthma, which comes along with wheezing, shortness of breath, and other lung function changes.

Read your pet shampoo labels, folks!