Hives (urticaria) in adults are triggered by some of the same factors that trigger hives in children and teenagers. Among these triggers or causes of hives in adults are allergic reactions. Adults may have allergies to such substances as medication, food, preservatives and pet dander. In allergic responses to these triggers (either from ingesting or touching the allergens), these adults develop hives on their skin within any amount of time between a few minutes and a few hours.

Allergic hives typically present as acute hives. As long as one is able to remove the allergen from his or her environment, the hives symptoms ultimately resolve and do not recur. If one should fail to identify the substance, then it is possible to be exposed to it again and again, resulting in hives episodes without relief. This could easily happen with a substance like food coloring or a food preservative. Most people are unaware that they ingest these substances when they eat processed foods. Hence, they are not likely to know which foods contain them or that they are repeatedly exposing themselves to allergens.

Autoimmune disease is another cause of hives in adults. Various autoimmune disorders, including lupus and thyroid disease, are associated with outbreaks of chronic hives. Some studies on the connection between hives and thyroid disease have shown greater prevalence of thyroid autoantibodies among patients with hives. Upon treatment for thyroid disease, these patients’ hives have cleared. The studies, therefore, indicate a definite connection between autoimmune disease and the development of hives, even though the mechanisms behind such a connection remain largely mysterious.

Stress and Infection as Triggers of Hives in Adults

Stress is yet another common trigger of hives in adults. This should not come as a surprise, given the high levels of stress endured by adults at their places of work and in other aspects of life. Younger age groups do experience stress. However, children tend to be shielded from the extremes of stress by the adults in their lives.

When urticaria in adults is associated with stress, it tends to present as a chronic condition. If the stress is not addressed, then the urticaria endures. In addition, chronic stress weakens the immune system, increasing patients’ vulnerability to infection and to psoriasis, an autoimmune disease which manifests as a skin condition.

Various infections, including viral, bacterial, fungal and parasitic infections can also be considered reasons for hives in adults. These infections vary. They may include urinary tract infections, infections of the gastrointestinal tract, ENT infections, upper respiratory tract infections and infections of the dental area. When these infections are successfully treated, the associated hives vanish, indicating that there is a connection between infection and the prevalence of hives.