Hives: Causes

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.