A 21-year-old man presented to the emergency department with a rash on his arms and neck (figure 1).
It had developed over the course of 36 h from discrete ‘pin prick’ areas of erythema into a maculopapular rash with vesicles (figure 2).
It covered his forearms from the dorsal aspect of the hands to the flexor surface of the elbows.
It was also beginning to develop around his neck (figure 3).
He described the rash as itchy and painful, and was feeling ‘under the weather’.
The patient had no previous dermatological or other medical history of note.
He took no medication.
He worked in a supermarket handling food items but there was no history of occupational chemical exposure.
He had not recently had any change in washing powder or personal hygiene products.
Physiological observations were entirely normal and systemic examination unremarkable.
Closer examination of the rash revealed that it was present only on skin exposed to the sun when wearing a short-sleeved shirt; the most striking feature was the ‘V’ shape on the patient's chest in keeping with the neck line of a polo shirt.
On further questioning the patient described a period of time 48 h prior to presentation (and 12 h prior to the development of the rash) spent strimming the grass under the hedges in his garden.
Blood tests including full blood count, urea and electrolytes, liver function test and C-reactive protein were all within normal reference ranges.
The list of potential differential diagnoses for a maculopapular rash is long, but given the distribution of the rash and the history of plant material exposure a diagnosis of phytophotodermatitis was made.
The patient was discharged with chlorphenamine, simple analgesia and the advice to wear a long-sleeved t-shirt and sunscreen when gardening in the future.
The rash resolved over a period of 3 weeks.
It remained pruritic throughout healing but the associated pain settled over a few days.
Residual scarring is beginning to fade 2 months after presentation.