Which type of chemical agent is known for causing skin blisters?

The type of chemical agent known for causing skin blisters is indeed classified as a blister agent. Blister agents are designed to cause blistering of the skin and mucous membranes upon contact. They typically penetrate the skin and lead to the formation of painful blisters, often accompanied by irritation, injury, and potential secondary infections. The most well-known example of a blister agent is sulfur mustard, commonly referred to as mustard gas.

In the context of the question, while other classes of chemical agents include nerve agents, which affect the nervous system; blood agents, which disrupt the body's ability to transport oxygen; and choking agents, which induce respiratory distress, none are specifically known for causing the characteristic blistering effect that defines blister agents. Hence, the choice that accurately identifies the type of chemical agent responsible for producing skin blisters is the one that mentions blister agents directly.