A bed bug rash can occur when you have been bitten by bed bugs.
The rash caused by the bites appears like a number of small hives. These hives tend to be in a cluster or orderly row pattern. The hives do itch like mosquito bites and in fact, like mosquitoes, bed bugs inject their saliva into the skin of the individual prior to biting. The saliva contains an anesthetic to keep the person from feeling the bite (so that the person stays asleep) and an anticoagulant in order to keep the blood from clotting so that it can be easily extracted from the human. The hives and redness and other symptoms are usually the body’s reaction to the saliva. Over the course of a few days after the biting has occurred, the hives will subside; leaving red marks that do not itch. These marks will eventually fade as well.
Sometimes the body reacts more aggressively towards the bed bug bites. If the body is allergic to the bites then the rash may be a general body rash. This may or may not be accompanied by more severe symptoms such as difficulty breathing and swollen lips or tongue. The allergic reaction to the bites may also be more localized. In this case the hives tend to be much larger and spread out more from the bite site than the typical bed bug skin rash. In addition, large puss-filled blisters often appear in the affected area.
If you are unfortunate enough to have been exposed and bitten by bed bugs, you can usually find the bedbug skin rash on the upper body, face, neck, and arms. However, bed bugs are not all that finicky and will bite any available area if they need to feed.
The resource diagnose my rash provides more detailed information on bug bites and skin rashes.
Additional bed bug information can be found below: