After speaking with the submitter, and viewing photos that she went back to the site and took for me, this was determined to be native cow parsnip. Cow parsnip does contain the same phototoxic compounds as giant hogweed, but in lower concentrations. The submitter's son (shown with the leg blisters) was playing in the patch of cow parsnip with friends and beating and breaking the plants.

Beth Myers-Shenai
June 16, 2017, 4:04 a.m.