DERMATITIS VENENATA 



III. THE URTICA GROUP. 



Urtica Subgroup. — This is characterized by containing its 

 poisonous principle in hairs. 



This group includes the nettles which belong to the genus Urtica 

 Linnaeus, of which U. urens is the common European type, while 

 U. ferox Forster is found in New Zealand, and U. pilulifera Linnaeus 

 occurs in the Mediterranean littoral. 



Laportea Gauducheau is an allied genus, of which L. crenulata 

 Roxburg in Bengal, L. stimulans Weddel in Java, and L. gigas 

 Weddel in New Holland, produce severe urticarial eruptions, 

 associated with pain lasting for several days. 



The genus Urera Gauducheau belongs to the same family, being 

 found in tropical Africa and America, while the genus Girardinia 

 Gauducheau is found in tropical Africa and Asia, and both contain 

 species with markedly urticarial properties. 



In all these the poisonous principle, which is said to be of the 

 nature of an aldehyde, is contained in a special poison apparatus, 

 which consists of secreting cells which pour their secretion into 

 awl-shaped filaments, or hairs which are filled with an acrid, non- 

 volatile, albuminoid, acid liquid. These hairs penetrate the skin, 

 and the tip, being broken in the process, discharges the poison into 

 the dermis. The poison quickly produces the well-known urticarial 

 eruption associated with itching, tingling, and even pain. 

 - Primula Subgroup.- — In the same group come quite a different 

 series of plants — viz., the primulas, primroses, etc.- — which belong 

 to the family Primulacese. In the tribe Primulese there is a section 

 called ' Sinesis,' which contdims Primula obconica Hsince, P . sinensis 

 Sabine, P. sieholdii E. Moir, and P. cortusoiides Linnaeus, which 

 possess poison glands associated with hard poisonous hairs, contact 

 with which produces acute dermatitis, which often begins as an 

 erythema on the face or back of the hands, and spreads quickly to 

 other regions. Soon the erythema becomes oedematous and swollen, 

 and vesicles may at times appear. The general aspect of the 

 patient with the red and swollen eyelids, red and swollen face, and 

 the similar eruption on other parts of the body, closely resembles 

 erysipelas, and is, without doubt, one of the forms of the complaint 

 often called ' the rose ' — i.e., a non-contagious erysipelas. 



It must, however, be admitted that some of the recurrent erup- 

 tions described on the hands and face of persons beheved to be 

 suffering from this or ivy-poisoning are suggestive of pellagra 

 (see p. 1700). The erythema of pellagra is, however, generally 

 confined to areas exposed to the light, and is usually associated 

 with some intestinal or nervous symptoms. It is, however, as well 

 to bear in mind the possibility of pellagra in cases of dermatitis 

 on the hands and face recurring in the spring or autumn. 

 ' The usual treatment is to apply calamine lotion, to which a 

 little menthol or opium is added. 



