Dear Penta-A, the rash
seems fairly innocuous & does suggest either some form of contact dermatitis
as you suggest (possibly to detergent or textiles) or a form of infection eg. scabies
. I suggest meeting a local dermatologist
& the problem is mild & easily sorted in either case. Large gatherings such as music festivals where people mingle or come into contact easily with each other are often harbingers of infections such as scabies or other insect borne skin ailments even insect bite reactions. it does require visual confirmation & a topical crotamiton
cream followed by a corticosteroid one after 3 days may resolve the rash completely. Do hope this helps. Visit your derma. Cheers!