Finding a "cause" for many with acute urticaria in most patients is not a reasonable expectation. It can be caused my infections, medications, other causes... but is generally idiopathic. If you have airway symptoms seek immediate care.Otherwise, see https://dermnetnz.org/topics/acute-urticaria
Inexplicable, itchy rash all over my body with no other symptoms (pics in the comment)20M, non-smoker, occasional drinker (3~4 times per month), no prescription medication. Hives started appearing all over my body two days ago, starting from my torso. (this was several hours after having a drink, just in case that matters) They respond well to cetirizine but return around 20 hours later. They seem to start spreading from different spots everyday: one day from my torso and then from my limbs. They itch quite a lot and some spots are tender to touch, but other than that there have been no other symptoms like any respiratory problem, sore throat or fever.While I am mildly allergic to dust mites, I've never had this kind of flareup that manifests itself on skin. I haven't eaten anything new or changed any laundry or skincare products either.