Vesicants are employed locally in chronic ulcers and to cause absorption of effusions into joints, or chronic thickening about them. When applied around the inflamed joints in acute rheumatism, they not only relieve the local affection, but appear to have a curative action on the general febrile condition.

In neuralgia, blisters over the painful point are useful, and sometimes, when neuralgia is in the side, or in the breast, it may be relieved by applying the blister over the corresponding part of the spine where there is usually a spot which is tender on pressure. In sciatica, the relief is often greater when the blister is applied to the heel, than over the nerve itself.

In neuralgia also it not unfrequently happens that a slight application of the actual cautery is more efficacious than a blister. The most convenient form of this is Paquelin's thermocautery.

In inflammation of the pericardium or pleura, a blister frequently relieves the pain, and it sometimes lessens or cuts short the inflammation. Applied over the epigastrium, blisters relieve vomiting arising from various causes.

In cerebral affections, such as obstinate headache, in meningitis and hydrocephalus, blisters to the nape of the neck or under the mastoid process are useful.

Hysterical paralysis of the limbs sometimes yields to blisters locally applied; and hysterical aphonia is sometimes removed by a blister over the larynx.