Each person reacts differently to a bed bug bite. Bite responses can range from an absence of any physical signs of the bite, to a small bite mark, to a serious allergic reaction. Bed bugs are not considered to be dangerous; however, some people may be allergic to bed bugs and can react adversely to the bites. Allergic symptoms that may require medical attention can include enlarged bite marks, painful swellings at the bite site, and, on rare occasions, anaphylaxis.