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. You may be able to pinpoint what causes it or you may to have to go for allergy testing.
Hope this helps.