Blister beetle dermatitis is a dermatitis caused mostly by cantharidin.


Cantharis is a blister beetle with dapples, slender legs, and cantharidin that can cause blisters of human skin and sharp pain.

Figure 1 cantharis

Signs and Symptoms

Cantharides usually fly out at night and neither bite, sting nor secrete venom when crawling on the human body. Once slapped or slightly compressed, amber, clear fluids containing cantharidin are immediately released from the front chest, knee joints, and genitals. There are burning sensation and sharp pain on the skin in few minutes. Bulla occurs in 8 - 12 hours. There is no inflammation around the bulla. If the insect body is crushed, the bulla is often very large. When the insect crawls on the skin, humans who are asleep often brush it off with their hands unconsciously. Until the next morning, the bulla or multiple blisters arranged in rows on the skin can be seen.

Figure 2 blister beetle dermatitis


The disease can be diagnosed on the basis of clinical manifestations.


The fluids in the bulla or blisters can be removed, and topical burn cream is appropriate.