In some instances it is probably due to the elimination of the drug through the cutaneous structures; in others, to the action of the drug upon the nervous system. The view that the drug acts as a toxin or generates some toxin or irritant material in the blood, to which the eruptive phenomena may be due, has also been advanced. [Illustration: Dermatitis medicamentosa. Bullous dermatitis from iodide of potassium.] #What is the character of the eruption in dermatitis medicamentosa?# It may be erythematous, papular, urticarial, vesicular, pustular or bullous, and, if the administration of the drug is continued, even gangrenous. #Name the more common drugs having such action.# Antipyrin, arsenic, atropia (or belladonna), bromides, chloral, copaiba, cubebs, digitalis, iodides, mercury, opium (or morphia), quinine, salicylic acid, stramonium, acetanilid, sulphonal, phenacetin, turpentine, many of the new coal-tar derivatives, etc. #State frequency and types of eruption due to the ingestion of antipyrin.# Not uncommon. _Erythematous_, morbilliform and erythemato-papular; itching is usually present and moderate desquamation may follow. Acetanilid, sulphonal, phenacetin, and other drugs of this class may provoke like eruptions. #Mention frequency and types of eruption due to the ingestion of arsenic.# Rare. Erythematous, erythemato-papular; exceptionally, herpetic, and pigmentary. Herpes zoster has been thought to follow its use. Keratosis of the palms and soles has also been occasionally observed, which, in rare instances, has developed into epithelioma. #Mention frequency and types of eruption due to the ingestion of atropia (or belladonna).# Not uncommon. _Erythematous_ and _scarlatinoid_; usually no febrile disturbance, and desquamation seldom follows. #Give frequency and types of cutaneous disturbance following the administration of the bromides (bromine).# Common. _Pustular_, sometimes furuncular and carbuncular and superficially ulcerative. In exceptional instances papillomatous or vegetating lesions have been observed. Co-administration of arsenic or potassium bitartrate is thought to have a preventive influence in some cases. #State frequency and types of cutaneous disturbance due to the administration of chloral.# Occasional. Scarlatinoid and urticarial, and exceptionally purpuric; in rare instances, if drug is continued, eruption becomes vesicular, hemorrhagic, ulcerative and even gangrenous. #State frequency and types of eruption following the administration of copaiba.# Not uncommon. _Urticarial_, erythemato-papular and _scarlatinoid_. #Mention frequency and types of eruption resulting from the ingestion of cubebs.# Uncommon. Erythematous and small papular. [Illustration: Fig. 14. A somewhat rare form of eruption from the ingestion of iodine compounds. (_After J.C. McGuire._)] #Mention frequency and types of eruption resulting from the administration of digitalis.#