This looks like urticaria or hives. Urticaria is usually triggered by allergens, such as drugs,
foods, insect bites, inhaled substances, in response to sunlight, cold, heat, stress, exercise, or a viral infection. Other common allergens are pollen, mold, dust, pet dander, or cosmetics. Since you experienced an itch, just go over these possibilities in your mind. Something may strike you. In many cases, hives clear up themselves and don’t require diagnosis or treatment.