Thanks for writing to us.
From the description it seems, you could be having a type of urticaria
known as dermatographism. Another plausible diagnosis, taking your japan visit in account is flagellate erythema
. It is seen with intake of a variant of mushroom known as Shiitake mushroom, which is commonly used in Japan. Hence it is also known as shiitake dermatitis
Urticaria would resolve with antihistamines alone while flagellate erythema may require oral steroids
The diagnosis can be made by clinically examining the lesions. For the same, you may consult a dermatologist
nearby or use ASK A SPECIALIST feature of this website.
Hope that answered your query.