Hi, welcome to the forum, it seems ore of urticaria but it can be associated with angioedema which is due to hypersensitivity reaction (type 1). Get your IgE levels estimated.
Drugs like amoxicillin, ACE inhibitors, stress, excitement, cold exposure, prolonged sitting or standing, and ingestion of certain foods can cause such reaction. This sometimes can be a emergency condition because there will be associated laryngeal edema leading to breathing problems.
It usually involves three types of attack like-
The skin including lips (cutaneous attacks)
The gastrointestinal tract (abdominal attacks) and
The larynx (laryngeal attacks)
Adrenaline, anti-histaminics and corticosteroids are the standard mode of treatment which should be taken after consultation from physician without delay. Take care and regards.