This section is from the book "Hartmann's Theory Acute Diseases And Their Homoeopathic Treatment", by Charles J. Hempel. Also available from Amazon: Theory of acute diseases, and their homoeopathic treatment.
§ 117. Petechia.
Petechias are of a violet, brown, black, and sometimes red colour, from one to two lines in diameter, generally round and circumscribed, though sometimes irregular and diffusing into the surrounding skin, with or without fever, (acute petechia?, petechial fever, chronic petechias). In some cases the spots-some at least - are several inches in circumference; these are called vibices, ecchymoses, and are, properly speaking, of the class of purpura haemorrhagica. They show themselves at irregular periods, first on the lower extremities, then on the arms and trunk: the face remains free, but not always the hands. At first the spots are of a bright-red, afterwards they assume a livid, and finally a brownish or yellowish aspect: this change can be seen most clearly by the new spots which continue to break out.
In some persons, the disease makes its appearance suddenly, at a time when the patients seem to enjoy good health; in others, it is preceded for weeks by pains in the limbs, which render the patient incapable of making the least exertion. Generally the disease is accompanied with great debility and lowness of spirits; the pulse is either small and feeble, or hard and frequent. Petechiae generally result from debility and from decomposition of the blood, and frequently occur as a symptom in putrid fever; sometimes they arise from keeping the skin too warm, and from getting overheated, hence they will occur in inflammatory fevers; they may likewise occur sympathetically in gastric and worm-fevers. They develop themselves like miliaria, and are frequently complicated with the latter disease.
If petechiae be a mere symptom of a more general disorder, the remedies prescribed for it have to be employed. The remedies which are most frequently indicated for petechias, are: Belladonna, Arsenic, Rhus t., Bryonia, Chininum, Ledum, Acid, sulph., Phosphor., Sec. corn., Silic, Laches., Aconite, Acid, phosph.