Causes and Risk Factors of Urticaria (Hives)

Urticaria, or hives, is a common type of rash characterized by the formation of raised, red, itchy bumps on the skin. Urticaria is commonly associated with an allergy to food, medications, and other irritants. Stress, infection, autoimmune disease, and even food poisoning can lead to hives.

The cause and severity of hives can vary from one person to the next. Urticaria can affect people of any age, gender, and race. It is estimated that between 15% and 23% of adults will experience at least one bout of urticaria in their lifetime. 

Allergic Reaction

Allergy is a common cause of urticaria. The red welts, itchy rash, and other symptoms are caused when the immune system responds abnormally to an otherwise harmless substance and floods the body with inflammatory chemicals including histamine.

Other symptoms include swelling (edema) and trouble breathing, which can become life-threatening in severe cases.

Three types of allergies are associated with urticaria:

• Food allergies, with common triggers including nuts, milk, eggs, soy, seafood, and wheat. About 90% of food allergies are related to these foods.
• Drug allergies, including those triggered by certain antibiotics (like cefaclor), anticonvulsants, antifungals (like clotrimazole), ibuprofen, or sulfonamides
• Seasonal and environmental allergies: Common allergens such as pollen, pet dander, insect bites, and latex also can cause allergy-related hives. Most of these allergy-induced hives will resolve on their own when the allergy trigger (allergen) is removed.

Common allergens such as pollen, pet dander, insect bites, and latex also can cause allergy-related hives. Most of these allergy-induced hives will resolve on their own when the allergy trigger (allergen) is removed.

Environmental Exposure

Hives sometimes occur when the skin rash is provoked by specific environmental or physical stimuli. Some of the causes of physical urticaria include:

• Water: Aquagenic urticaria is a rare form of hives caused by contact with water.
• Sunlight: Solar urticaria is caused by exposure to ultraviolet (UV) light.
• Heat rash: Sometimes called cholinergic urticaria, it is caused by sweaty or hot skin.
• Cold: Rarely, cold can cause hives after exposure.
• Friction: These dermographic urticaria are caused by friction or the firm stroking of skin.
• Pressure: Urticaria can occur when excessive pressure is exerted on the skin, such as when you carry a heavy bag on your shoulder.
• Vibration: These hives form due to vibration, including mowing the lawn or clapping.

The same inflammatory response seen with allergic hives is at work with physical urticaria but the rash and welts may look different. They may form only at the site of contact or exposure, or they may cause a systemic response that includes symptoms such as headaches, low blood pressure, flushing, and fainting. These types are more likely to be a chronic condition that recurs.

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Stress

Stress is commonly associated with the development or worsening of chronic hives. There's a significant number of people with chronic urticaria (35% to 60%) who have a co-occurring mental health condition, including anxiety and depression.

It's not entirely clear why there is a relationship between mental health and urticaria. In some cases, it may be a physical exposure like stress-related perspiration that leads to a heat rash.

It's also important to consider that having a chronic urticaria diagnosis and living with its symptoms can be the reason for why people are stressed or depressed, too.

Exercise

Physical activity can cause urticaria to appear in some people. The cause remains unknown, although it's common for another co-occurring food allergy to be present.

Symptoms typically occur within 30 minutes of starting to exercise. In food-dependent cases, symptoms occur only when both eating a particular food (like wheat) and then exercising shortly after. In some cases, this can lead to a potentially life-threatening exercise-induced anaphylaxis.

Infections and Diseases

There are certain infections and diseases for which urticaria is common.

This is especially true for young children in whom 80% of hives are caused by a viral infection. The activation of the immune response may be triggered by something as simple as a cold. The hives tend to develop within a week of infection and usually resolve in a week or two without treatment.

Other illnesses are commonly associated with hives, many of which are autoimmune and others of which are related to an infection or malignancy. They include:

• Chronic kidney disease (CKD)
• Dermatitis herpetiformis, an autoimmune disorder of the skin related to celiac disease
• Hashimoto’s thyroiditis, an autoimmune disease associated with low thyroid function
• Helicobacter pylori, a common bacterial infection of the stomach
• Hepatitis B, a viral infection of the liver
• Hepatitis C, a chronic viral infection of the liver
• Lupus, a systemic (whole-body) autoimmune disorder
• Lymphoma, a type of blood cancer
• Parasitic gastrointestinal infections, like Giardia lamblia and Anisakis simplex
• Polycythemia vera, a slow-growing cancer of the bone marrow
• Rheumatoid arthritis, an autoimmune form of arthritis
• Sjögren's disease, an autoimmune disorder affecting moisture-producing glands
• Type 1 diabetes
• Vasculitis, the inflammation of blood vessels that has both autoimmune and non-autoimmune causes

Hives associated with these diseases can be chronic (long-lasting) or acute (sudden and for a limited time).

Diagnosis

With urticaria, diagnosis is focused on identifying the cause. This can involve assessing an allergy to food, medication, or environmental exposures through skin prick or other testing.

In some cases, over-the-counter medications like Claritin (loratadine) can help to treat symptoms. Prescription drugs or additional therapies may be needed.

If an autoimmune disorder or other medical cause is at work, your healthcare provider will consider additional testing and treatment options.

Summary

Hives are a common allergy response to foods, medication, or environmental exposure. The itchy rash and red welts also can occur with chronic autoimmune conditions, infections, and other medical causes.

Treatment will vary depending on the cause. Be sure to seek immediate medical care if you also experience swelling that closes the airway, problems breathing, heart rate changes, or other symptoms associated with a severe allergic response known as anaphylaxis.