There is a lot of confusion and misinformation about bedbugs and whether or not dogs can spread them. So let's set the record straight: yes, dogs can spread bedbugs. Here's how it works:
Bedbugs are attracted to warmth and carbon dioxide, which is why they often bite people while sleeping. But they'll also bite animals if given a chance. When a bedbug bites an animal, it injects saliva into the wound.
This saliva contains anticoagulants that keep the blood flowing so the bug can feed for longer. The problem is that this anticoagulant keeps the bitten animal from properly clotting its blood. So when a dog with bedbug bites scratches themselves, they can spread their own blood around - and with it, any bedbugs that might be hiding in their fur.
Of course, not every dog that comes into contact with bedbugs will end up spreading them. It depends on how much the dog scratches and whether or not they have an open wound that could serve as an entry point for the bugs' saliva. But it's something to be aware of if you think your home might be infested with bedbugs.