Blisters grow on your arms when the weather is hot. How's it going?

It may be herpes simplex, which is a small blister on the hand in summer. I also have a medicated bath prescription here: 30g of Xanthium sibiricum, 60g of alum, 2000ml of water, soaking for 1000ml, decocting to obtain liquid medicine1000ml, fumigating hands while it is hot, and then soaking twice a day for 30 minutes each time, and it can be cured in 5 days.