Skin disease... what in the world is this?

A nine -year old girl was brought in by her mother with the complaint of itchy lesion around her mouth  for about a week then later the right corner of the mouth became ulcerated. They have been to a clinic and the lesion had not improved.

Dry,ulcerated lips and corner of mouth of a 9-year old girl

The girl looked sullen, obviously unhappy with her appearance. On further questioning there appeared to be no systemic problems like loss of appetite, recent weight loss, fever or any other medical conditions. I asked about allergy history and it seemed no evidence of this. What about lipstick? The mother said the child had not started to use it. I did think of the girl being assaulted in the mouth but there was no evidence of a bruise.

Then my attending nurse asked the girl whether she had been sucking at pickled mangoes sold by street vendors. Then the mother recalled that the girl had eaten a lot of pickled mangoes and she noticed the mouth had swollen. The girl admitted of it being itchy and she kept rubbing at it ( and I guessed they must have applied some over-the- counter medications as well). She must have been allergic to the chemical used to pickle the mangoes, a kind of contact dermatitis. She was treated along that line.