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The historical common principle was to identify and destroy a superficial fungal parasite, remove material harbouring it and prevent reinfection. Modern diagnosis preserves this principle for genuine fungal infection, but rejects its indiscriminate application to “tinea decalvans”. The three labels must therefore be discussed separately.

In pityriasis versicolor, look for finely scaling patches of altered skin pigmentation, commonly on the trunk. Examine superficial skin scrapings by microscopy when uncertain. Historically, washing, removal of loose scale and a topical “parasiticide” aimed to reach the organism in the outer epidermis. Today pityriasis versicolor is associated with overgrowth of Malassezia yeasts already present on the skin; it is not ordinary contagious ringworm and is not evidence of poor cleanliness.^[ref] Topical ketoconazole or selenium sulfide can control it. Extensive or recurrent disease sometimes needs other treatment. Loss of scale and control of the yeast need not immediately restore skin pigmentation; residual colour can persist for weeks or months. A Wood's lamp can assist examination, but is not a substitute for the whole clinical assessment.^[ref]

“Tinea decalvans” is the critical historical trap. Some nineteenth-century writers interpreted patchy baldness as parasitic and advocated extraction of affected hairs followed by prolonged topical treatment. A January–June 1867 digest explicitly calls the condition contagious and reports a mercury(II) chloride preparation. That is evidence of a contemporary belief, not evidence that the proposed organism caused every case of patchy baldness.^[ref] The label often covered what is now called alopecia areata, an immune-mediated form of hair loss. Smooth bald patches require differentiation from scaly patches with broken hairs and demonstrated fungal infection. Confirm the diagnosis before treating. In established alopecia areata, a period “parasiticide” is inappropriate: observation or diagnosis-specific treatment, including local corticosteroids in suitable cases, is considered instead. Neither mercury(II) chloride nor destructive epilation is a modern treatment for alopecia areata.^[ref]

For contagious ringworm, establish the site and extent. An enlarging scaly ring on bare skin suggests tinea corporis; scaly bald areas with broken hairs suggest tinea capitis. Examine scrapings or hairs by microscopy and, where appropriate, fungal culture. Clean clothing, towels, combs and brushes; avoid sharing them and investigate relevant human or animal sources. These measures address transmission, while an antifungal drug treats the affected tissue.^[ref] Limited tinea corporis can often be treated topically. Tinea capitis needs an oral antifungal drug, such as griseofulvin or terbinafine chosen for the circumstances, because a cream alone does not clear the infected hair-bearing site. An adjunctive shampoo can reduce spread but does not replace systemic treatment. Unsupervised corticosteroid cream can mask or worsen ringworm.^[ref][ref]

Thus the useful unifying idea is cause-directed treatment that reaches the affected tissue, with transmission control when infection is transmissible. It does not follow that all three nineteenth-century names denote the same class of disease, or that every bald patch requires killing a parasite.

The guide is the diagnosis and the physiological cost of persistent vomiting, not the symptom alone. Establish whether material is truly vomited, search for local and extra-gastric causes, correct depletion and then treat the cause. A distinction between vomiting, passive regurgitation and rumination syndrome prevents several different disorders being forced into one category. First assess inability to retain fluid, weight loss, dehydration, gastrointestinal bleeding, severe abdominal pain or distension and neurological signs. Significant danger requires prompt investigation and support before a prolonged trial of symptom remedies.^[ref]

The history should establish duration, relation to meals, retained undigested food, pain, nausea, the character of the material, bowel function, weight change, pregnancy possibility and exposure to drugs or ethanol. Delayed large-volume vomiting of food with weight loss suggests retention, but does not distinguish gastric outlet obstruction from impaired emptying by itself. Early postprandial discomfort, haematemesis or an abdominal mass changes the investigation. Bilious vomiting with distension and failure to pass stool raises concern for gastrointestinal obstruction. Headache, visual disturbance or focal neurological signs directs attention beyond the stomach; kidney disease, metabolic disturbances and pregnancy are also possible causes. None can be chosen as the diagnosis from the short source question alone.^[ref]

An 1867 physician could already distinguish suspected gastric ulcer, chronic gastritis, cancer, obstruction near the pylorus, pregnancy-related vomiting, uraemia and “sympathetic” vomiting accompanying disease elsewhere. The therapeutic reasoning was to remove a provoking dietary or medicinal cause, adapt food to what could be retained, investigate an obstructive or destructive lesion and address the associated systemic disease. Symptom suppression alone could conceal continued starvation. A 1867 digest reproduces an account of opium controlling vomiting in advanced consumption. It establishes an example of period palliation, not proof of cure and not a general prescription for chronic vomiting.^[ref]

Modern investigations are chosen by that differential: examination and appropriate blood tests for depletion or systemic disease, a pregnancy test where relevant, endoscopy for a suspected upper digestive lesion, and imaging when gastrointestinal obstruction is possible. Gastroparesis specifically means delayed gastric emptying without mechanical obstruction. After excluding obstruction, demonstrate abnormal emptying rather than diagnosing it from vomiting alone. A standardized gastric emptying scintigraphy follows a labelled meal with a gamma camera; serial measurements test how much remains in the stomach. This apparatus addresses a physiological question that simple inspection of vomited food cannot answer.^[ref]

Treatment then branches with the diagnosis. Obstruction needs decompression and treatment of the obstructing lesion; escalating an antiemetic does not remove it. A confirmed peptic ulcer may require Helicobacter pylori eradication, proton pump inhibitor treatment and withdrawal of an ulcer-provoking nonsteroidal anti-inflammatory drug where possible. A suspected malignant lesion needs tissue diagnosis and appropriate specialist treatment.^[ref] In confirmed gastroparesis, smaller suitable meals, nutritional planning, correction of a contributing diabetes problem and selected prokinetic or antiemetic treatment have distinct purposes: an antiemetic may reduce nausea without accelerating gastric emptying. Persistent nutritional failure may require feeding beyond the stomach.^[ref]

Medication-induced vomiting, metabolic disease, pregnancy-related illness and central causes require their own treatment pathways. Fluid and electrolyte losses need assessment and correction throughout. Reassess intake, weight and function as well as the frequency of vomiting. If no structural or metabolic explanation is established, investigate the relevant disorder of motility or gut–brain interaction on positive criteria; “nothing found yet” does not justify either a fabricated diagnosis or a dismissal of the symptom.