Bed bug infestations can be detected by the presence of bug feces and cast skin on the mattress or the bed. They usually bite on the exposed part of the body, like shoulders, neck, face, and arms. Bed bug bites look like flat or raised areas that become itchy, inflamed or blistered. The reaction after their bite might not appear immediately, but you’ll start seeing the symptoms after a few days. However, everyone doesn’t react in the same manner to the bed bug bites.