Hello
Thanks for posting your query.
I can understand your concern. I reviewed the picture.
Though I could see a few blisters I couldn't appreciate the entire length of the rash. It looks as if it could have followed even an insect bite. Since its not on any other part of the body, I am ruling out a drug reaction which wouldnt have just been localized to the wrist. This kind of rash could even occur as a contact dermatitis.
I would recommend visiting a dermatologist who can thoroughly examine it, which i am unable to do online.
Meanwhile you can apply cortisone cream mixed with mupirocin cream twice daily. In case of itching, you can administer an anti histamine.
Please let me know if you have any queries.
Take care