For an account of the source, properties, composition, and cathartic effects of croton oil, see page 587. We are here to consider it as an external remedy.

Local Effects

When croton oil is rubbed on the skin, or simply kept in contact with it, after a considerable time, sometimes sooner, sometimes later, but generally in the course of a day or two, it produces a diffused redness of the surface, which is attended, almost from the beginning, with a countless crop of minute eczematous vesicles. These increase, become pustular, run together, and at length, if the application be continued, form one complete pustulated surface, with considerable swelling. Upon a cessation of the application, the inflammation abates, and the pustules soon form crusts, which after a time fall off, leaving the surface somewhat discoloured, but not otherwise deranged. But the difference of susceptibility to the effects of croton oil is very remarkable, and much more striking even than in the case of tartar emetic. I have seen persons whose skins I could scarcely affect with the oil by the most diligent efforts; and I have repeatedly seen others, in which it has acted with extraordinary violence, causing intense inflammation in the seat of application, and sometimes even far beyond it. in several instances, I have seen the face and eyes violently inflamed from croton oil rubbed on the back; and, though it is probable that the fingers of the patient may have conveyed it from one point to the other, I have been unable to trace the connection.

Therapeutic Application

The oil may be used as a revulsive agent, whenever the case is so far chronic in its character as to admit of a slow operation in the remedy. Several days must be allowed for the production of its full effect. it is generally used in chronic internal inflammations, particularly the pectoral, in rheumatic and scrofulous swellings, and in other indolent tumefactions. The particular affection in which I have derived most advantage from it is chronic laryngitis, in which, if properly applied, it is probably as effectual as tartar emetic or repeated blistering, and on the whole more convenient.

Croton oil would seem to be strongly indicated in cases of internal disease, which has followed the disappearance of an eruption upon the surface. There may be peculiar relations between eruptive cutaneous affections and the constitution generally, differing from those of simple diffused inflammation; and it is, therefore, not impossible that disorder, resulting from or connected with the disappearance of an eruption, may be relieved by the artificial production of another eruption, where the inflammation of a simple rubefacient or blister might fail. Upon the same principle, the oil may be used in internal irritations which may be supposed to depend upon constitutional causes, ordinarily giving rise to a cutaneous eruption. Thus, patients sometimes complain of great gastric uneasiness, and various internal distress, perhaps dyspnoea, perhaps cardiac disturbance, which have come rather suddenly upon them, and for which they cannot account. At length an eruption occurs, urticaria for example, and they are completely relieved of their internal sufferings. Whenever symptoms of this kind, of some duration, suggest to the practitioner such a connection with an eruptive tendency, there is a fair indication for the use of croton oil. it is preferable to tartar emetic, for meeting this indication, because less severe, and because it can be extended over a wider surface, and thus bring a greater degree of this particular eruptive influence into operation. The proper place for applying the oil, if there has been an eruption, would be its former seat; if none, the outside of the arm above the elbow.

Method of Application. it is always proper, when the peculiar susceptibilities of the patient are not known, to begin with a mixture of one part of the croton oil with four parts of olive or almond oil. if this should not act, the strength may be gradually increased, until, if found necessary, the undiluted oil may be employed. Sometimes the weakest acts energetically, and, in other cases, the strongest scarcely at all. The oil should be applied by friction, once, twice, or three times daily, according to the urgency of the case, and the peculiar susceptibility; and in the mean time a piece of flannel saturated with it may be kept in contact with the surface. When the full effect has been produced, the oil must be suspended; but, in order to sustain its influence, and it often ought to be sustained for months, the oil must be frequently reapplied. in the intervals, the surface may be dressed with simple cerate, or, if very much irritated, with cold cream {Unguentum aquae rosae).

The British Liniment (Linimentum Crotonis, Br.), in which one measure of croton oil is mixed with seven of olive oil, is, according to my personal observation, too feeble, and will often fail of causing pustu-lation, though it would, no doubt, act in peculiarly sensitive persons.*

* M. Trousseau derives great advantage from the local application of croton oil in alleviating the sufferings of dropsical patients, in whom the effusion in the limbs and elsewhere is so great as to cause much uneasiness and threaten serious evils, and in whom the use of diuretics and other anti-hydropic remedies has proved unavailing. The following is the mode of proceeding, as described by M. Merceau in the Annuaire de Therapeutique (1865, p. 195). The patient is to be sitting in an arm-chair, with his feet resting on a cushion, covered with several folds of cloth, and placed on the floor. Gentle friction is to be made on the legs below the knee, with from 150 to 450 grains of croton oil, according to the degree of effect desired, by means of a roll of linen, or, what is better, of soft leather or skin, and continued till all the oil has been used. On the following day, if no effect be apparent, the same process is to be repeated; and three or four applications of the oil may be made, should the eruption not appear. The limbs are to be well covered after each application, and great care observed that the patient shall not take cold. it is absolutely essential to success that the patient remain in the arm-chair, day and night, for an indefinite time, even for several months if necessary. The eruption takes place as in health, and gives rise to a copious discharge, which speedily reduces the size of the limb, and otherwise relieves the patient. The danger of resuming the horizontal posture is that the discharge soon ceases with the healing of the eruption, and the patient may suffer greatly from the rapid accumulation of the serous liquid in the interior cavities. Gangrene occurred only in one instance of all in which the remedy was used, and in this was superficial and limited, and of little account. it is useless to apply the oil above the knee. {Note to the third edition.)