Possibly allergic to house? Any advice on how to handle before making an offer?

After seeing about 30-40 houses, we've finally found a house in budget and target location that both of us really like. Our market is tough (very competitive) and we are ready to move fast, but have one unfortunate hangup: both times I've visited (two separate showings, a private viewing and went back for the open house in different days/times/weather), my knees became hot, swollen, and patchy red within 15 mins of the visit. Both times, it resolved about 20 minutes after leaving, and hasn't happened anywhere else. A few details: No direct contact with plants, no kneeling, no crouching or known contact with anything in the house Arms and shoulders (also exposed) were unaffected - just knees Others with me had zero reaction Not heat-related as far as I can tell - I walked a couple miles in the neighborhood afterward in the same conditions and the reaction died down with no issue I don't have any confirmed allergies or known conditions; though this isn't incredibly uncommon for me and has happened a small handful of times over the last 5-7 years with no common thread (e.g., a few times on different vacations, once at a friend's place that has never resurfaced on other visits, maybe even a couple times during my everyday routine, etc). It's uncomfortable but not painful and has resolved itself - my doctor hasn't seemed concerned due to the sporadic nature and healthy labs. The fact that this has happened both times in the house is the first real identifiable pattern and of course concerning for such a big decision & commitment. We otherwise love the house and would be putting in an offer already if not for this. Has anyone dealt with something like this during a home search? Random ideas I've had, though unsure how realistic or if there are any other avenues to explore given our inexperience: Seems unusual to ask about pets, cleaning chemicals, lawn treatments etc - especially given I really have no definitive leads on what could be the trigger...? Is it totally unreasonable to ask for another private viewing and split walkthrough (yard-only vs. house-only vs. garage/basement-only) to try to isolate the cause? Maybe during the inspection period? Would a standard inspection contingency realistically let us back out if we determine it's something tied to the property that's expensive/impossible to fix? Is there a more specific contingency we could reasonably write in the offer given this situation? Has anyone actually identified something like this (mold, pet dander in flooring, lawn treatment residue, cleaning chemical, etc.) during due diligence, and how did you go about isolating for it? Appreciate any real-world experience - trying to be thorough before we commit in a market where we don't have a ton of time to spare.