What causes Hives?
When you have an allergic reaction to a substance, your body releases histamine and other chemicals into your bloodstream. This causes itching, swelling, and other symptoms. Hives are a common reaction, especially in people with other allergies such as hay fever.
When swelling or welts occur around the face, especially the lips and eyes, it is called angioedema. Swelling from angioedema can also occur around your hands, feet, and throat.
Many substances can trigger hives, including:
Animal dander (especially cats) Insect bites Medications Pollen Shellfish, fish, nuts, eggs, milk, and other foods
Hives may also develop as a result of:
Emotional stress Extreme cold or sun exposure Excessive perspiration Illness (including lupus, other autoimmune diseases, and leukemia Infections such as mononucleosis </s>