A medicinal plaster should be regarded as the general and most important remedy in all cases of (inflammatory) swelling. We shall presently discuss the nature of plasters to be used in each specific form of disease. A bandage plays a more important part (than a medicinal plaster) as regards its healing and curative efficacy, inasmuch as it materially contributes to the purification and healing of an ulcer and keeps the joints steady. A medicinal plaster should be applied from down upward or in a direction contrary to that of the local hair (Pratiloma). It should never be applied (so as to run down with the local hair), since a plaster, applied as directed above, would firmly stick to the surface of the affected part, and naturally percolate through the follicles of the hair and the external orifices of the vehicles of perspiration (Sudoriferous ducts), thus permeating the organism with its own native potency and virtue.
A medicinal plaster should be removed or replaced by a fresh one as soon as it has become dry, except in cases where the purpose of its application would be found to be the drawing of pus to a definite head (Pidayitavya Vrana).
A dried medicinal plaster will prove useless or abortive, and may act as a caustic or corrosive agent. A medicinal plaster admits of being grouped under any of the three subheads of Pralepa, Pradeha and Alepana (according to its thickness or consistency) etc.
A medicinal plaster of the Pralepa class is applied thin and cold, and is made to be endued with an absorbing (Vishoshi) or non-absorbing (Avishoshi *) property according to the nature of the effect desired.
On the other hand, a medicinal plaster of the Pradeha class is applied either thick or thin, warm or cold, and acts as a non-absorbent.
A medicinal plaster of the Alepana class stands midway between a Pralepa and a Pradeha.
Of these, a plaster of the Pralepana class is possessed of the efficacy of pacifying or restoring the deranged blood and Pittam to their normal condition. A plaster of the Pradeha class pacifies the deranged Vayu and Kapham and tends to bring about the union, purification, and healing (of an ulcer), causing the subsidence of pain and swelling. Hence it should be used in all types of swelling whether ulcerated or otherwise.
* As in the case of a Pidayitavya ulcer, described before, where the withdrawing or gathering of pus to a definite head is desired.
A medicinal plaster (Alepanam) applied over an ulcer is called by the changed epithet of Kalka or Niruddha-Alepanam (arrestive or astringent plaster). The function of such an Alepanam consists in arresting a local haemorrhage, in softening the ulcer, in withdrawing sloughing or putrifying flesh from its cavity, in checking the formation of pus in its inside, and in correcting the morbid matter or deranged humours (that retard its union and healing).
A medicinal plaster of the Alepanam class would prove beneficial in a swelling marked by the absence of suppuration, inasmuch as it subdues the characteristic symptoms of each of the deranged bodily humours viz, the burning sensation (peculiar to the deranged Pittam), itching (incidental to the deranged state of Kapham) and the aching pain (which marks the disorder of the bodily Vayu). Its action lies principally in cleansing the skin, the flesh and the blood of all morbiferous diatheses, in removing the burning sensation, and in alleviating the piercing pain and itching.
A physician (surgeon) should use an Alepana in (ulcerous) diseases appearing about the anus, or about any other vital part (Marmas) of the body, with a view to bring about the purification of the (local deranged humours). In diseases caused by a deranged condition of the Vayu, Pittam or Kapham, medicinal plasters should be respectively mixed with a quantity of clarified butter, measuring a sixth, quarter, and an eighth part of their respective quantities.
It has been said that the thickness of an Alepa-nam should not be made to exceed that of the newly-flayed skin of a buffalo. Under no condition, should a medicinal plaster be applied at night, inasmuch as such a measure would arrest the escape or radiation of heat from the swelling in virtue of its own inherent humidity, and thus bring on an aggravation.
In diseases, which are amenable to the application of medicinal plasters of the Pradeha type, as well as in swellings resulting from the vitiated condition of blood and the Pittam, or in those which are of extrinsic origin, or are due to the effect of a poison or blow, the plaster should be applied cold, by day. A plaster should not be applied without removing the previous one, nor over the one applied on the day before, as this would increase the local heat and aggravate the pain and the burning sensation on account of its greater or increased thickness. A medicinal plaster, previously used, should not be moistened and applied again; it should be held as absolutely ineffective owing to its virtue having been previously used or soaked in. *