DYSTROPHIES 



3231 



Erythema Solare. 



The effects of sunlight on the skin, including the histology of the 

 lesions, have already been discussed in Chapter HI., pp. 83-85. 

 They are caused by the active effects of the rays at the violet end 

 of the spectrum. The vSkin of the parts exposed becomes 

 erythematous, swollen, and vesicles and bullae may appear. 

 Desquamation follows, and the skin is often left pigmented 

 (sunburn) . 



The treatment consists in applying calamine lotion, and later any 

 bland ointment such as simple cold cream. 



Dermatitis Solaris. 



After repeated attacks of erythema solare — or at times without 

 any history of such— the skin of the hands and exposed parts 

 in planters and other people living an outdoor life in the tropics 

 becomes slowly reddened, and may be slightly rough to the touch. 

 Freckles and hyper pigmented spots are generally present, and not 

 rarely small telangiectasia. In a later stage warty patches often 

 appear, and the dermatitis, as noted by McLeod, may somewhat 

 resemble the dermatitis produced by X rays. Atrophic changes 

 may also develop. The condition, which is also known by the term 

 tropical skin, is somewhat similar to what Unna called ' seaman's 

 skin ' and to senile atrophodermia or biotripsis (seep. 2282). 



Diagnosis. — The diagnosis from pellagra has already been dis- 

 cussed (see p. 1730) . 



Prognosis. — The dermatitis is very obstinate, but generally 

 becomes cured spontaneously in a cold climate. 



Treatment. — A change to a temperate chmate is the only effica- 

 cious treatment. Exposure to the sun is to be avoided as much as 

 possible. 



Chloasma. 



Chloasma, which, as is well known, is characterized by the presence 

 of dark brownish or dirty yellowish patches, situated commonly 

 on the face, is of frequent occurrence in the tropics in Europeans 

 as well as natives. The patches are plainly distinguishable in the 

 skin of Indian and Sinhalese natives, though in African negroes 

 they may be indistinguishable. The condition may be due to 

 several causes, and the following types may be mentioned : — 



I. Chloasma solare (melasma solare), due to exposure to the 

 sun. A similar condition may be due to exposure to a powerful 

 light or glare of any kind, and may even occasionally develop in 

 people who pass a long time on glaciers and fields of snow. Chloasma 

 solare is found among Europeans, half-castes, and also in natives. 

 In natives who wear clothes it is easy to see that the parts exposed 

 to the sun are darker. The condition is generally found on the 

 face, and it may be diffuse, or one or two small patches only may 

 be present. The colour varies from a slight yellowish-brownish 



