How to Diagnose Urticaria and Hives

urticaria diagnosis
© Verywell, 2018 

Diagnosing the underlying cause of urticaria, or hives, whether it is acute or chronic, is important to help manage symptoms, to decrease recurrences, to guide treatment decisions, and most importantly, to prevent possible complications.

One in five people will experience urticaria least once in their lifetime. The condition is marked by red itchy welts that can appear anywhere on the skin.

These welts, also known as wheals, can last for minutes to hours but can recur over several weeks.

Most of the time, urticaria is self-limited and benign. When flare-ups last longer than six weeks, this is known as chronic urticaria. While these type of hives affect only one percent of people, they can have a negative impact on quality of life.

Medical History

In most cases, the cause of urticaria is obvious. If you are stung by a bee and break out in hives, you have your answer. In a similar way, most cases are diagnosed based on your history and clinical symptoms.

A study in the World Allergy Organization Journal reviewed 82 medical articles and recommended an urticaria checklist for your doctor that includes the following:

  • Dates, times, and duration of hives
  • Depression, anxiety, or stress
  • Family history of hives
  • Dyspepsia or peptic ulcer disease (H. pylori infection)
  • Foods, especially if you have tried something new
  • Medications and supplements, both prescription and over-the-counter
  • Menstrual cycle (a rare form of chronic urticaria flares-up 7 to 10 days before your period)
  • Physical trigger (cold, exercise, heat, sunlight)
  • Recent infections (common cold, GI bug)
  • Work exposures (chemicals)

You may want to bring a log with this information to your office visit.

Physical Exam

Unless you have hives at the time of your office visit, your physical exam is often not going to help make a diagnosis. That is the case unless you have dermatographism.

Dermatographism is a clinical sign associated with physical urticaria (hives that are caused by physical exposures) and atopic dermatitis. If you have dermatographism, a wheal forms when your skin is rubbed or stroked in a certain area. Your doctor will provoke this response by stroking your skin with a clean, firm object. A wheal will appear within six to seven minutes and start to fade 15 to 30 minutes later.

Labs and Tests

Lab tests are not always needed to diagnose urticaria. They are more helpful if you have certain symptoms or triggers.

Looking for Food Allergies

Food allergies do not only increase your risk for hives. They can also cause angioedema or in the worst case scenario, anaphylaxis. It is important to avoid exposures to foods that could trigger a life-threatening reaction.

Your doctor may order one of the following tests if they suspect a food allergy:

  • Enzyme-linked immunosorbent assays (ELISA): An increase in IgE antibodies is a hallmark of allergies. In an ELISA test, an antigen from a specific food is added to a blood sample. If you are allergic to that food, you will have IgE antibodies in your blood against those antigens. They will bond together in the blood sample, and you will get a positive test result. The test is easily performed in a laboratory and is relatively inexpensive. It is also an excellent option for someone who is unable to tolerate a skin prick test.
  • Radioallergosorbent test (RAST): ELISA tests have mostly replaced RAST. The RAST also measures IgE antibodies by adding a specific allergen to the blood sample. The main difference is that it uses a radiolabeled IgE antibody to interpret the final results.
  • Skin prick tests: A small amount of an antigen is scratched into the skin with a needle and you are monitored for a local reaction. If a test is positive, you will develop a small red pump over the area, usually within 20 to 30 minutes. This test is performed in your doctor's office in the case that you have a severe reaction that requires treatment. To get more accurate results, it is important not to take any antihistamines a week before your test.

    These tests can also be used to screen for allergies to other triggers, not just food.

    Looking for Autoimmune Disease

    As many as 40 to 45 percent of chronic urticaria cases are associated with autoimmune diseases like celiac disease, lupus, Sjogren syndrome, rheumatoid arthritis, and type 1 diabetes. It is even more strongly associated with autoimmune thyroid diseases like Graves' disease and Hashimoto's thyroiditis, which accounts for at least 10 percent of those cases.

    If your doctor suspects an autoimmune condition, he may screen with some of the following blood tests:

    • Antinuclear antibody (ANA)
    • C-reactive protein
    • Sedimentation rate
    • Thyroid stimulating hormone (TSH)

    Abnormal findings on these tests could lead to other more specific tests based on the condition suspected: transglutaminase antibodies for celiac disease; anti-dsDNA, anti-Smith, and complement for lupus; anti-cyclic citrullinated peptide (anti-CCP) and rheumatoid factor for rheumatoid arthritis; and anti-SSA/Ro or anti-SSB/La for Sjogren syndrome.

    It is usually not enough to check thyroid function alone. In eight percent of cases, chronic urticaria is attributable to autoimmune thyroid disease but thyroid function is normal. For this reason, your doctor may also check for the presence of thyroid antibodies, specifically thyroglobulin antibody (anti-Tg) and thyroid peroxidase antibody (anti-TPO).

      Looking for Infection

      Numerous studies have shown that urticaria can be associated with infections from bacteria, viruses, and parasites. Infections may cause acute or chronic urticaria. Some viral infections in children, but not adults, have an increased risk of acute hives. These viruses include adenovirus, enterovirus, rotavirus, and RSV.

      Most Common Infectious Causes of Urticaria. (a) = acute, (c) = chronic
      BacteriaParasitesViruses
      • H. pylori (c)
      • Plasmodium (a)
      • Staphylococcus (a) (c)
      • Streptococcus (a) (c)
      • Yersinia (c)
      • Anisakis (a)
      • Blastocytsis (a) (c)
      • Giardia (a)
      • Strongyloides (c)
      • Toxocara (c)
      • Cytomegalovirus (a) (c)
      • Epstein-Barr (a) (c)
      • Hepatitis A or B (a)
      • Hepatitis C  (c)
      • Influenza (a)
      • Parvovirus B19 (a)

      Thankfully, most viral infections and their hives are self-limited. Chronic infections, however, may lead to chronic urticaria and require treatment. Lab tests may be necessary to make a diagnosis.

      Lab screening often begins with a complete blood count. A high white blood count could be a sign of infection and an increase in eosinophils, in particular, could indicate that a parasitic infection is to blame. In this case, a stool specimen should be collected to screen for ova and parasites.

      Serology measures antibodies in the body against certain pathogens, indicating that you have been infected, or at least exposed to, that organism. There are serologic blood tests available for many of the bacteria and viruses listed above. Anti-streptolysin (ASO) checks for antibodies against Streptococcus. 

      H. pylori can be tested for with serology but there are two other ways to screen for it that may be more accurate. 

      • Stool antigen test: H. pylori lives in the stomach. Antigens from the bacteria are excreted into the stool and can be detected in a stool sample using an immunoassay.
      • Urea breath test: H. pylori breaks urea down into carbon dioxide and ammonia. After you ingest a urea tablet or liquid that has trace amounts of a radioactive carbon attached, you are asked to breathe into a container. The test detects H. pylori based on the presence of carbon isotope in your exhalation.

      Looking for Physical Causes

      Physical urticaria accounts for 20 to 30 percent of all chronic urticaria. In this case, exposure to a certain environmental trigger can cause hives to form.

      To make a diagnosis, your doctor may want to mimic the physical stimulus in a controlled environment. He may also try to establish how much of that stimulus you can tolerate before developing symptoms. This will allow him to provide practical advice on how to minimize and manage symptoms.

      These are the most common physicals triggers your doctor could test for based on your history: 

      • Cold: Cold urticaria is a condition where cold air, liquids, or objects cause hives. Your doctor may perform the ice cube test, where an ice cube in a plastic bag is applied to the forearm over five minutes. A reaction usually occurs within 10 minutes of removal.
      • Exercise: Some people develop hives with exercise. This could be from the exercise itself or from the increased core body temperature that occurs with exercise. Your doctor may have you exercise on a stationary bicycle or on a treadmill to induce symptoms.
      • Heat: Local heat can sometimes cause wheals to form. Heat provocation testing is performed by putting a glass cylinder filled with 44°C water or a metal cylinder at 50°C to 55°C against the arm for five minutes. Hives develop within several minutes.
      • Pressure: There is a form of delayed dermatographism where swelling of the skin occurs four to six hours after pressure is applied, although it can occur anywhere from 30 minutes to 12 hours afterward. It can happen anywhere on the body where clothes are tight, on the buttocks with prolonged sitting, or on the feet after extended walking. A doctor may apply a 10-pound weight to your arm for 20 minutes. You will be asked to monitor for a skin reaction over the next 24 hours.
      • Sunlight: Solar urticaria is rare and develops on uncovered skin within minutes of exposure to direct sunlight. Provocation testing is carried out by exposing small defined areas of the skin to ultraviolet (UV) lamps with UV-A and UV-B filters.

      Testing is most accurate if you are not on antihistamine therapy at the time.

      Skin Biopsy

      Skin biopsy is rarely needed but it can be helpful if there is a concern for urticarial vasculitis. This is not actually a form of urticaria but can mimic it in appearance. A difference is that skin lesions are often described as burning rather than as itchy.

      This condition is much more serious than classic hives because it can affect multiple organ systems, including the gastrointestinal tract, kidneys, lungs, and muscles.

      Differential Diagnosis

      Hives have a variety of causes, ranging from allergies to autoimmune disease. Cold or hot temperatures, exercise, sunlight, and even tight clothes can cause a flare-up. Chronic infections, like H . pylori or hepatitis C, have also been associated with urticaria. With a diagnosis, it is important to differentiate between true hives and urticarial vasculitis, which can look similar but can have serious complications.

      Sources:

      Cherrez-Ojeda I, Robles-Velasco K, Bedoya-  P, et al. Checklist for a Complete Chronic Urticaria Medical History: An Easy Tool. World Allergy Organ J. 2017 Oct 3;10(1):34. doi: 10.1186/s40413-017-0165-0.

      Kasumagic-Halilovic E, Beslic N, Ovcina-Kurtovic1 N. Thyroid Autoimmunity in Patients with Chronic Urticaria. Med Arch. 2017 Feb; 71(1): 29–31. doi: 10.5455/medarh.2017.71.29-31.

      Saini S. Chronic Urticaria: Clinical Manifestations, Diagnosis, Pathogenesis, and Natural History. In: Feldweg AM (ed), UptoDate [Internet], Waltham, MA. Updated June 29, 2017.

      Schoepke N, Doumoulakis G, Maurer M. Diagnosis of Urticaria. Indian J Dermatol. 2013 May-Jun; 58(3): 211–218. doi: 10.4103/0019-5154.110831.

      Wedi B, Raap U, Wieczorek D, Kapp A. Urticaria and Infections. Allergy Asthma Clin Immunol. 2009; 5(1): 10. doi: 10.1186/1710-1492-5-10.