Dirt is not bad for dogs.
If your dog is eating dirt it may be because the dog is lacking some nutrients such as Iron in it's diet and is eating the dirt to get those nutrients.
Or the dog may just like eating the dirt.
There's nothing bad about a dog eating dirt and the dog will not be harmed when eating dirt.
So you can safely allow the dog to eat dirt and they will be just fine.
My dog eats dirt sometimes as well and he's just fine.
Even kids and toddlers eat dirt and they are not harmed in doing so.
I've eaten dirt as a kid until around 5 years old and never got sick from it.