These blister beetles are feeding on goldenrod  pollen (Solidago sp.).  I had these beetles crawling all over my hands and never experienced any skin irritation. Indeed, they seemed not at all concerned with me. They sure poop a lot !

Blister Beetle adults feed on leaves in the tops of a plant but are especially attracted to flowers where they feed on nectar and pollen. These beetles are mid to late summer insects, active in mid-July and early August . The beetles pictured here are part of a large conglomeration of insects feeding on Goldenrod, Solidago spp. at the Winfield Mounds Forest Preserve at Winfield, IL. USA.

Female blister beetles lay clusters of eggs in the soil in late summer. The small, active larvae that hatch from these eggs crawl over the soil surface entering cracks in search for grasshopper egg pods. On finding a grasshopper eggmass, the larvae become immobile and spend the rest of their larval time as legless grubs. The next summer they pupate soon emerge as adults. Blister beetle populations follow closely the abundance of grasshoppers the year previous.

Blister Beetles produce Cantharidin, a poisonous substance comparable to cyanide and strychnine in toxicity. The substance is very stable and remains toxic in dead beetles. Animals may be poisoned by ingesting beetles while grazing or eating harvested silage. Cantharidin can also cause severe skin inflammation and blisters. It is absorbed through the intestine and can cause symptoms such as inflammation, colic, straining, elevated temperature, depression, increased heart rate and respiration, dehydration, sweating, and diarrhea. There is frequent urination during the first 24 hours after ingestion, accompanied by inflammation of the urinary tract. This irritation may also result in secondary infection and bleeding. The concentration of cantharidin in adult beetles depends primarily on the sex; males produce the chemical and only pass on small amounts to the females during mating. Cantharidin amounts also depend on species; the striped blister beetle has approximately five times more catharidin than the black variety.