I have had occasion to use this drug especially for patients who show the peculiar modality of relief in Cloudy/wet weather and aggravation in sunny weather. The other red letter symptom is constipation - passes stools standing up. A couple of burns cases with strictures have also benefited from this drug.
 

CAUSTICUM- Tinctura Acris Sine Kali Chemical                           PROVER: Dr. Hahnemann MIASM: Psora, Syphilis, Sycosis
A/F	Burns, fright, suppressed eruptions, Paralysis of single parts.
MIND	Grief, sadness. Cares for others. Weeping easy. Slow learner, easy falling. Insanity. Rebellious. Compulsive neurosis. Serious, idealistic, sensitive, Hurried.
CHILDREN	Passes stool standing up. Slow learners
HEAD	Confusion, intoxication, vertigo as if falling. Empty sensation between skull & brain> warmth
FACE	Arthritis of joints. Bells Palsy R. side
EYES	Warts on lids. Sense as if dilating. Pain like sand. Inflammation, ulceration. Sparks,mist, insects before eyes. Drooping. Photophobia
EARS	Loud noise foll.by deafness. Otalgia, Otorrhea. Echoes.
NOSE	Warts. Epistaxis <am, blowing.
THROAT	Painless hoarseness<exertion. Cracking, Sense of constriction/swelling-urge to swallow. Dry but thirstless.
STOMACH	Desires-cold drinks, beer. Averse sweets. Eructation of food. Vomits food, blood.
ABDOMEN	Pressure of clothes<.Tympanitic< eating.
RECTUM	Constipation with straining, red face> standing. Hemorrhoids large impede stools. Fistula, Fissure, abscess in anus
URINARY	Frequent, scanty,involuntary <bed in. Itching meatus. Hematuria
MALE	Increased desire, no erection. Red spots on penis. Itching. Smegma.
FEMALE	Cracks around nipples. ↓milk. Menses< daytime. Leucorrhea<night. Inertia in labor. Averse  coition
RESPIRATORY	Hoarse Cough<talking, cold air, evening, coffee. >cold water. Expect. Scanty, ropy, soapy- must swallow. Hoarseness of speakers – paralysis of chords. Cannot cough deep enough
EXTREMITIES	Deformities around joints. Rheumatism. Cramps. Pain hip joint. Unsteady walk, tendency to fall in children.
SKIN	Dirty white sallow. Warts. Rough, large horny
GENERALS	Burns. Paralysis of single parts, Periodicity, Cracks & fissures, Epistaxis, hematuria. Deformity < joints
PECULIAR SYMPTOMS	Empty sensation in head>warmth. Stands to pass stool. Paralysis of single parts. Cough > cold drinks. Periodicity. Sympathetic to others. Choreic movements like intercourse.
THREAD	Slow progressive diseases. Paralysis of single parts. Contractures. Clear weather<. Damp wet >. Serious idealistic, sensitive, Sympathetic