My daughter is scared of the dog?

Everyone in my family love dogs. But when we go over to my brothers house, my four year old little girl gets scared out of her mind. My brother has a 260 pound English mastiff, the dog is really sweet. But for some reason my little girl doesn’t want to be anywhere near the dog. From day one, she has just been terrified of the dog, she was really hesitant to meet the dog the first time, she did it. But then I noticed that she was afraid.

why is this? We have a border collie at home and they get along and play together just fine. When my brothers dog starts barking or stands up, or just walks near her, my daughter will run to me wanting to be picked up. She doesn’t even want to be in the same room as the dog, even when I’m holding her In my arms, she doesn’t want me to go anywhere near him.

of course I respect my daughter and I make sure she feels safe. But why is she like this?

My brothers dog has done nothing wrong. Why is she acting so scared of him? Like I said we have a border collie at home and they play together.