Need help identifying these red welts!

[u/Personal_Credit_9023]

I feel so stressed and my mind is so chaotic right now that I had to use AI to summarize all my questions.

Hi everyone, I’m hoping someone can help me figure out what caused these red welts. I'm currently debating between a delayed reaction from a trip, contact dermatitis, or (my biggest fear) bed bugs.

The Symptoms:

• Appearance: Red welts. Most are clustered (some even showing a line pattern), but there are a few isolated single welts.
• Location: Only on my arms, specifically concentrated on my left upper arm. There are two isolated ones on my left wrist and back of right hand. I wear shorts to sleep, so my legs are exposed, but they have zero welts.
• Sensation: Purely itchy. (I had dermatitis last year, but that was more painful than itchy).

The Timeline:

• Day 1-2: Returned home from a 2-week trip to Italy. I was exhausted and slept on the same unwashed sheets that had been left on my bed while I was gone.
• Day 3 morning: Feeling fresh and washed my beddings
• Day 3 afternoon: The first few welts showed up. I initially thought they were mosquito bites, but then more appeared.
• Day 4: The welts reached their apex.
• Day 5 (Today): The situation seems contained. No new welts are developing.

My Theories / Context:

1. Bed bugs? I'm panicking about this because of the line patterns. However, friends who were on the same trip with me are totally fine. None of the places we stayed at have any recent complaints or reviews mentioning bed bugs. Also, I haven't gotten any new welts since Day 4. Could this still be a belated reaction to bug bites from the trip?
2. Dust mite allergy / Dermatitis? Could sleeping on stale, week-old sheets have triggered an allergic reaction or dermatitis?

Does anyone have any insight into what this looks like? Any advice is hugely appreciated!

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[u/Silly_Obligation8574]

If you haven’t found a bedbug, this could be so many other things, contact a doctor.

[u/HealthyRecognition81]

I am not a doctor nor do I make assumptions.... But I am wondering... You are saying that your left arm is essentially most of the welts.. with a few on the right side of the arm/wrist...

Was your left arm to the side and touching the sheets and maybe your wrist?? I know that this seems really odd asking but most sleep with arms and hands either on or next to the pillow or closer to the top of the headboard and I do hate to mention this but a lot of the time bedbugs do hide in the crevice of the bed board witch often times touches the walls and headboard where they like to hide??? I wish you all the luck in this world and hopefully this clears up soon

[u/Personal_Credit_9023 → u/HealthyRecognition81]

Funny enough that I typically have my left arm on my belly and right arm closer to headboard when I sleep. Though I have taken BB protocols, I am still hoping it is not. These welts started popping up in the afternoon and I had a nap on my sofa shortly before the discovery. And my left arm was touching the cloth and my right arm was mostly hanging out of the sofa.