What Is Causing The Welts On My Body?

About half an hour ago I felt itching in my jeans at my thigh & reached in to scratch. A couple minutes later it started again on my hip. I took off my pants & sent my husband for the bactine. I decided to throw them into a hot washer & met him in the bath for the bactine & that when I saw two HUGE welts. TOOK PIX. One is fist size & the other is larger. I scratched above & below to confirm they were not caused from my scratching. I never saw anything like it. 54 5'8" 160. Currently wearing a heart monitor.