My daughter just got back from a school trip to Arizona and she has itchy bites all over her legs. They stayed in a dorm-like hostel and I think it had bed bugs. How can you tell if a bite is from a bed bug? K. H., Boston, MA

You can’t. The reason is that people react differently to bites and stings from insects, not just bed bugs. Bed bug bites can look different on different people. Some people are just more sensitive to the bed bug’s saliva that causes the reaction, and some have no sensitivity at all. Most people have reactions ranging from a slight reddish mark to a swollen, inflamed wheal (bump), which may itch intensely for days.

Reactions and Response Times Are Highly Variable

The length of time from bed bug bite to reaction also varies greatly among individuals. For those with little sensitivity to the bite, a reaction may not be noticed for as long as 11 days after the bite. It seems that most people do not react to their first bed bug bite at all, but their immune system becomes increasingly sensitized with each subsequent bite. The skin reaction becomes more obvious and the length of time from bite to reaction decreases with each additional bite until the reaction can be almost immediate. About 15% of individuals, however, never show a response to repeated bed bug bites.

There is No Consistent Description of Bed Bug Bites

If forced to describe a “typical” bed bug bite, we could say that it would have at least some of these characteristics:

• A slightly reddish lump or swelling that may also form a blister
• No red spot in the center of the bump as with some other biting insects
• Bites most common on arms, shoulders, and neck, but may occur elsewhere, including on the face.
• Bites sometimes grouped in a triangle or line.
• Bites often itch, ranging from moderate to intense, typically lasting from a few hours to a few days.

Misdiagnoses of bed bug bites are common, even by physicians. Other insect bites, certain medical conditions, and even environmental irritants can all mimic bed bug bites. The only way to confirm that a suspected bite was caused by a bed bug is to have a professional inspection that finds actual bed bugs or some other evidence of a bed bug infestation.

Photo Credit : “Bedbugb2” by James Heilman, MD – Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons.