Hives are pale, itchy welts that occur singularly or in groups on any part of the skin. Hives can appear and disappear quickly, lasting a few days or a few weeks. According to the American Academy of Dermatology, hives are common, occurring in 10 to 20 percent of the population at some point during their lifetime. Varying in size, hives can appear as small bumps or as larger swellings, formed by the joining together of smaller bumps.
Stress
Chronic emotional or physical stress can cause the immune system to falter, Hives.org notes. A weakened immune system releases histamine to attack and stop the stressor. Though histamine cannot eliminate stress, it can cause an outbreak of hives on the body. Histamine production can occur due to an immune response to suppressed emotions, sunlight, soap, shampoo, lotion, fabrics, exercise, sweat and extreme temperatures. Pet dander or insect bites can also cause an immune reaction resulting in an outbreak of hives.
Food Allergies
Food allergies and food sensitivities can cause hives. The common food culprits include shellfish, eggs, milk, nuts, chocolate, berries and tomatoes. Food additives such as sulfites and salicylates, preservatives and other chemicals may trigger an outbreak, the Mayo Clinic notes.
Medications
The American Academy of Dermatology states that many medications, both prescription and over-the-counter, can cause hives. Over-the-counter medicines like non-steroidal anti-inflammatory medications, including aspirin, ibuprofen and Advil can trigger hives in some people. Diet pills, vitamins, herbal supplements, diuretics, and antacids may cause an allergic reaction, which can result in hives. Taking prescription medicines like antibiotics, blood pressure medicines, sedatives and pain medicines can result in hives.
Underlying Conditions
An overactive immune system or underlying autoimmune diseases, including thyroid disease, lupus, leukemia or lymphoma, can produce antibodies that may cause hives. The Mayo Clinic notes that infections like hepatitis, upper respiratory viruses or even the common cold may over-stimulate the immune system resulting in an outbreak.
