Allergic reactions, particularly to foods and medications, are another common cause of acute hives. Generally speaking, hives that occur as a result of eating certain foods almost always appear within a few minutes to a few hours of eating the food. Reactions to medications may occur after the first dose, or not until the medication has been taken for a week or two.
Stress is a common cause that acute and chronic hives share. You may not feel particularly stressed, but your body may, especially if you are very busy. Life stressors that can result in hives may be positive or negative.
Other than stress, the causes of chronic hives are quite different when compared to the causes of acute hives. Allergies only cause about 5 to 10% of chronic hives cases. When allergies cause chronic hives, pet allergy is usually to blame. Pollen, mold or dust mite allergies only rarely cause chronic hives.
Chronic infections, such as viral hepatitis, sinus infections and urinary tract infections, can cause chronic hives. Some studies have shown that infection with Helicobacter pylori, a bacteria commonly connected with stomach ulcers, is also associated with chronic hives.
Metabolic diseases, such as low or high thyroid function, liver disease and kidney disease, may also be at the root of chronic hives. In addition, it appears that a large percentage of people without an obvious trigger for their chronic hives actually have an autoimmune disease -- a condition in which the immune system attacks healthy tissue, including skin.
Use of certain medications, particularly non-steroidal anti-inflammatory drugs (NSAIDs), are also associated with chronic hives.