You do not have to be bitten by a blister beetle to receive blisters. When the blister beetle is rubbed, pressed, flicked off or squished, its defense is its blood that is released. This hemolymph carries the cantharidin and causes you to blister without even being bitten. Blisters usually do not occur on the fingers or hands because the skin is thicker. Irritation mainly develops on more sensitive areas such as the neck or arms. Some individuals are more sensitive than others and can immediately develop blisters while other individuals never develop them.