The sudden appearance of pimples or lesions on the face and body could be due to an allergic reaction, insect bites, or exposure to environmental irritants during the trip. Since it developed overnight and involves widespread areas, further evaluation is recommended to rule out conditions like urticaria or other skin reactions.
Next Steps
I suggest an online consultation for a detailed assessment and guidance on treatment to alleviate discomfort and prevent worsening. I am happy to assist you further.