25 y/o male presents to outpatient psych appt with the above | Figure 1

25 y/o male presents to outpatient psych appt with the above photos and inquires about this rash. Pt states rash appears without apparent cause 2-3 times a week and disappears with 24-48 hrs. Rash was originally confined to L arm, but pt reports it appears to spread further with each appearance and now shows up on bilateral upper extremities. Pt denies #Pruritus or pain. Pt reports rash is raised and blanchable. Advised pt to f/u with PCP, but curious as to the workup and ddx?

Similar cases

Non-itchy rash continuous over pts body from head to toe. No response to steroids, antibiotics, antihistamines, or topical creams. Any ideas??

all over rash on patient this weekend, puritic, circular spots. Pt used Benadryl last night, and most of rash resolved--returned on fingers, under breasts, and groin area--and again puritic. Thoughts?

USCG Doc here, 24 y/o male presented with nonpruritic rash onset this am, no known exposure to chemicals or any other agents. I treated with 25mg Benadryl thinking urticaria this morning and he reported this afternoon spreading rash to chest and buttocks. Thoughts?

20 years old female with new onset rash 5 days ago. The lesions appear in trunk, extremities and face and are pruritic. They usually appear at night and resolve completely in less than 24 hours. The patient reports swollen lips the first day of the rash. No other complaints. The patient reports having a similar rash 10 years ago, which resolved in half an hour. Complete blood count and basic biochemical analysis are normal.