All inflammatory conditions of the skin due to contact with deleterious substances such as caustic, chemical irritants, iodoform, etc., are included under this head, but the most common causes are the rhus plants--_poison ivy_ (or _poison oak_) and _poison sumach_ (_poison dogwood_). Mere proximity to these plants will, in some individuals, provoke cutaneous disturbance (_rhus poisoning_, _ivy poisoning_), although they may be handled by others with impunity. Many other plants are also known to produce cutaneous irritation in certain subjects; among these may be mentioned the nettle, primrose, cowhage, smartweed, balm of Gilead, oleander, and rue. The local action of iodoform (_iodoform dermatitis_) in some individuals is that of a decided irritant, bringing about a dermatitis, which often spreads much beyond the parts of application, and which in those eczematously inclined may result in a veritable and persistent eczema. #Describe the symptoms of rhus poisoning.# The symptoms appear usually soon after exposure, and consist of an inflammatory condition of the skin of an eczematous nature, varying in degree from an erythematous to a bullous character, and with or without [oe]dema and swelling. As a rule, marked itching and burning are present. The face, hands, forearms and genitalia are favorite parts, although it may in many instances involve a greater portion of the whole surface. #What is the course of rhus poisoning?# It runs an acute course, terminating in recovery in one to six weeks. In those eczematously inclined, however, it may result in a veritable and persistent form of that disease. #How would you treat rhus poisoning?# By soothing and astringent applications, such as are employed in acute eczema (_q. v._), which are to be used freely. Among the most valuable are: a lotion of fluid extract of grindelia robusta, one to two drachms to four ounces of water; lotio nigra, either alone or followed by the oxide-of-zinc ointment; a saturated solution of boric acid, with a half to two drachms of carbolic acid to the pint; a lotion of zinc sulphate, a half to four grains to the ounce; weak alkaline lotions; cold cream, petrolatum, and oxide-of-zinc ointments. #How would you treat the dermatitis due to other deleterious substances of this class?# By applications of a soothing and protective character, similar to those used in eczema and burns. #Dermatitis Medicamentosa.# #What do you understand by dermatitis medicamentosa?# Under this head are included all eruptions due to the ingestion or absorption of certain drugs. In rare instances one dose will have such effect; commonly, however, it results only after several days' or weeks' continued administration. With some drugs such effect is the rule, with others it is exceptional, nor are all individuals equally susceptible. #How is the eruption produced in dermatitis medicamentosa?#