Urticaria (hives) usually starts with a red, itchy patch of skin and develops into a raised welt with clearly defined borders. It is caused by an abnormal immune response. While this typically occurs as a result of an allergy to a food or medicine, there are non-allergic causes. Symptoms may come and go quickly or be longer-lasting. Appearance may be enough for diagnosis, but chronic cases may require allergy testing, a physical challenge, or other tests. Antihistamines are typically used to treat urticaria, although H2 blockers, corticosteroids, antidepressants, and anti-asthma drugs may also be prescribed.
Urticaria can affect people of any age and develop on any part of the body, including the palms and soles.
The hives will appear as raised welts (wheals or weals) and will invariably be itchy, some more than others. They can vary in shape and size but will have a clearly defined border. When pressed, the center will “blanch” (turn white).
Symptoms are commonly confused with those of other conditions, but close attention to these defining factors can help distinguish urticaria.
Most hives are acute and self-limited, resolving on their own within 24 to 48 hours. Others may take days or weeks before they fully resolve. During this time, it is not uncommon for the hives to disappear and reappear. Urticaria may sometimes be accompanied by a deep-seated swelling of tissue known as angioedema, most commonly affecting the face, lips, tongue, throat, or eyelids.
Chronic hives can persist for months or even years and may be triggered by stress, heat, cold, and other physical triggers.
Urticaria differs from eczema (atopic dermatitis) in that eczema is characterized by dryness, crusting, blistering, cracking, oozing, or bleeding. Hives are not typically described in these ways.
Urticaria is caused by an inflammatory reaction that prompts capillaries in the dermis (the layer of tissue just beneath the outer skin) to leak fluid. When this happens, the accumulation of fluid results in a defined area of raised skin that persists until the fluid is eventually reabsorbed into the surrounding cells.
Hives have specific characteristics that set them apart from other skin conditions:
- The elevated area of skin has a clearly defined border.
- When you press the rash, it will “blanches” (turns white).
- They will be itchy, sometimes intensely so. There may also be paired with pain or a burning sensation.
- They can appear on anywhere on the body and change shape, move around, disappear, and reappear over short periods of time.
- When they resolve, the skin will return to normal without scarring.
- Most will not be accompanied by systemic reactions such as fever, nausea, muscle aches, joint pain, or headaches.
Urticaria is classified as being either acute or chronic depending on the duration of the eruption. Acute hives last for less than six weeks, while chronic hives extend well beyond six weeks.
Acute urticaria is more common in children and young adults. The majority are classified as idiopathic, meaning that we don’t know the cause. Most cases are self-limited; individual lesions tend to resolve on their own within a few hours. An eruption rarely lasts more than several days, although it may recur over weeks. If a cause is found, it is usually related to an infection, insect bite, or a food or drug allergy.
Chronic urticaria, by contrast, often requires medical treatment. In one 2014 study, 75 percent of people with chronic hives had symptoms that lasted for longer than a year, while 11 percent had symptoms for five or more years. In half of the cases, the offending agent was never found.
Urticaria is known to affect up to 20 percent of the population and strikes people irrespective of age, race, or gender. Hives most often appear in the evening or early morning just after waking. Itching is typically worse at night, often interfering with sleep.
Diagnosing the underlying cause of urticaria, or hives, whether it is acute or chronic, is important to help manage symptoms, decrease recurrences, guide treatment decisions, and most importantly, prevent possible complications. Your doctor will review your medical history, perform a physical exam, and may run tests that aim to detect food allergies, infection, autoimmune disease, or physical causes.
While many forms of urticaria can resolve after the cause is eliminated, others may require further treatment. Getting to the bottom of what is causing your hives is the first step in determining the outcome of your case.
Most times, the cause of urticaria is obvious. If you are stung by a bee and break out in hives, for example, 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 seven to 10 days before your period)
- Physical trigger (cold, exercise, heat, sunlight)
- Recent infections (common cold, gastrointestinal bug)
- Work exposures (chemicals)
You may want to log this information and bring it to your office visit.
What you think are hives may actually be something else. Your doctor may be able to tell the difference between different skin conditions during a physical exam. For example, scabies, an infection caused by a mite that gets under the skin, can cause itching and raised red spots too. Unlike hives, however, scabies bites tend to localize at skin folds, i.e., between fingers, at the flexion points over your wrists, elbows, and knees, and along the genitalia. Even the dry inflamed skin in eczema can sometimes form blisters that can be confused for hives. Based on the appearance of your skin, your doctor will decide whether to pursue tests for those conditions.
Unless you have hives at the time you see your doctor, 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.
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 he or she suspects a food allergy:
- 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 case 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.
- Enzyme-linked immunosorbent assay (ELISA): An increase in IgE antibodies is a hallmark of allergies. In an ELISA test, your blood is drawn and an antigen from a specific food is added to the sample. If you are allergic to that food, IgE antibodies against those antigens will be present (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): The RAST also measures IgE antibodies by adding a specific allergen to a blood sample. While it may be used, ELISA tests have mostly replaced this option.
Most cases of acute urticaria are allergy-related. Chronic urticaria (hives lasting over six weeks or recurring over months or years) is believed to be caused by an autoimmune response. In both cases, the hives are caused by a substance or condition that the body reacts abnormally to.
The reaction may be triggered by any number of things, including foods, drugs, pollen, or substances like latex or nickel. Even certain physical triggers—such as heat, cold, pressure, sun, exercise, and vibration—can set off an immune response that leads to the formation of hives.
Simply removing yourself from the trigger may be enough to provide relief. By and large, acute hives are self-limited and will usually resolve within hours or several days without treatment.
If the hives are especially itchy, you can use a wet, cold compress to soothe the itch and reduce swelling. The simplest way to do this is to soak a washcloth in a bowl of ice water and apply it directly to the skin.
To further ease the discomfort, wear loose clothing either made of cotton or a smooth, lightweight synthetic like rayon. Avoid wool, linen, denim, or any textured fabric that can irritate the skin. You should also avoid getting overheated, as this can exacerbate symptoms. And, whatever you do, do not scratch.
Antihistamines are the best, first-line treatment for hives. These drugs work by suppressing histamine, a chemical produced by the immune system that instigates the symptoms of allergy. For most types of urticaria, an over-the-counter (OTC) antihistamine may provide ample relief.