Hives: Causes Make an Appointment Refer a Patient Ask a Question Reviewed by Christine B. Cho, MD (April 01, 2019) What causes hives (urticaria)? No identifiable cause: In many cases, no cause is identified, and the hives are thought to occur spontaneously. This form of hives is often called Recurrent Spontaneous Urticaria or Chronic Idiopathic Urticaria. It has a good prognosis. Most cases resolve over time. The hives can recur more frequently or more severely with concurrent infection, stress, heat and NSAID or alcohol use. Allergies: When hives are caused by allergies, they happen immediately (within minutes) of being exposed to the allergen. Foods , such as milk, egg, wheat, soy, peanut, tree nuts, fish and shellfish. Eating a particular food and then exercising can cause food-dependent, exercise-induced hives and/or anaphylaxis (a life-threatening reaction) Medications, such as penicillin and other antibiotics, vaccines, sulfa drugs and aspirin. Aspirin may cause a delayed reaction hours later. Insect stings from bees, wasps, yellow jackets or fire ants Environmental allergies (typically through contact), such as cat or dog saliva Occupational contact, such as cow dander, natural rubber latex, flour, grains, feeds, enzymes and a variety of plant and animal species Contrary to popular belief, laundry detergents and lotions are not a common cause or trigger for urticaria. Physical causes: Pressure, friction, heat, sweat, cold, water, sunlight and vibration Many of these triggers can be made worse by stress, alcohol and/or NSAID use. Underlying autoimmune, infectious or inflammatory diseases: Viruses, bacteria (streptococcus, mycoplasma) and parasites Thyroid disease, hepatitis, lupus (systemic lupus erythematosus) or some types of cancer; these are much less common. Hives: Diagnosis Clinical Trials For more than 100 years, National Jewish Health has been committed to finding new treatments and cures for diseases. Search our clinical trials.