Bed bugs feed primarily on human blood, but can be found on bats, rabbits, domestic animals, and other warm-blooded mammals. They also have the ability to survive long periods of starvation and adverse temperatures. Bed bugs are mentioned in early European history and literature and are believed to have been transported around the world by clothing and bedding. Today, they are found in both temperate and tropical regions. These bugs have the potential to carry diseases, but there is not any evidence that they have ever transmitted disease. Some people are not affected by bed bug bites, but others can have an allergic reaction to the bug's saliva resulting in uncomfortable itching and red welts. Dried blood, fecal spots, and a sweet odor may indicate bed bug infestations.