CLR and other CLR products are toxic to dogs, especially if they ingest it or if the CLR comes into contact with the dogs skin or eyes.
Some CLR products such as CLR Clear Pipes and Drains is designated as a safer choice by the EPA, and is considered non toxic, the other CLR products like CLR Calcium Lime & Rust Remover is toxic and is designed to be toxic.
Because CLR Calcium Lime & Rust Remover is designed to be toxic, it can cause burns to the eyes, skin and respiratory tract of dogs and humans and even cats and other pets.
If the product is ingested it can cause oral burns, gastrointestinal disturbances, vomiting and possibly death in both dogs and humans as well as cats.
CLR Clear Pipes and Drains cleaner is designated as the safer choice by the EPA and is considered to be non toxic for people and pets.
And some other CLR Products like the Mold & Mildew Remover, while it's not as toxic as CLR Calcium Lime & Rust Remover can still cause mild skin irritation or even gastrointestinal upset if ingested by humans, dogs, cats and other pets and animals.
If a dog ingests any CLR product you should seek immediate veterinary attention.
And if the dog has skin or eye contact with the CLR products, you should immediately rinse the skin or eyes with water and seek veterinary advice if irritation persists.