How Are Hives (Urticaria)cDiagnosed?

Hives—also known as urticaria—is an inflammatory skin condition characterized by red or skin-colored welts on the body. It causes itchiness and is sometimes accompanied by larger patches of swelling (angioedema). Hives can be short-term (acute) and resolve within six weeks—with or without treatment. In some cases, it can last longer, known as chronic urticaria.

Proper diagnosis of hives is essential for the medical management of this condition, which may be treated by a primary care physician, dermatologist (a doctor who specializes in skin conditions), allergist (a doctor who specializes in allergic conditions), or another healthcare provider. This typically involves a physical examination and an assessment of medical history. Additional tests may be needed for confirmation and to determine the severity and type of urticaria.

It’s important to understand how urticaria is diagnosed, including the details of the tests that may be involved as well as how conditions with a similar presentation are ruled out.  

Medical History

The first step of diagnosis typically involves a thorough and comprehensive evaluation of your medical history and status. The healthcare provider will ask about:

• The size, shape, and location of the bumps (called weals) as well as any larger areas of swelling
• How long you’ve been experiencing symptoms
• How severe your symptoms are and any other unusual signs you’re experiencing
• Any prescribed or over-the-counter medications you’re taking, especially nonsteroidal anti-inflammatory drugs (NSAIDs), antibiotics, and hormone therapies
• Any recent travel you’ve done
• Any other medical or skin conditions you’ve had
• Personal or family history of allergies or allergic disorders
• Sexual health and any sexually transmitted infections (STIs)
• Signs of underlying diseases, such as fever, weight loss, joint stiffness, arthritis, abdominal pain, bone pain, and heat or cold sensitivity
• Any bug bites or bee stings

In addition, your primary care provider, allergist, or dermatologist will need to screen for any aggravating factors that may worsen hives. This step will help them determine if you have inducible urticaria, a type that’s set off by environmental stimuli. This means discussing:

• Any physical or environmental triggers, such as whether symptoms are worse after hot showers, heat or cold exposure, due to sweating, or after eating certain foods
• Whether you’re taking NSAIDs, which can trigger hives in some people
• Stress levels and mental health status
• Dietary habits, including if you’re eating spicy foods or rich meals
• Any known allergies
• Alcohol consumption habits  

Physical Exam

Following a discussion of your symptoms, your healthcare provider will perform a physical exam for your condition. They will look for any symptoms on your eyes, ears, nose, throat, lymph nodes, abdomen, and musculoskeletal system. This is critical for ensuring that symptoms are indeed those of hives and not of other conditions.

Your healthcare provider will also check your vital signs by measuring your heart rate, blood pressure, respiration, and body temperature. Certain symptoms, such as wheezing, fever, pain, scaling, and blistering, are signs of other conditions.

Additionally, they will test for dermatographism, also known as dermographism, which is a common sign of hives. This is when, after applying pressure on the skin, weals form in the shape of what has applied that pressure within minutes. Typically, providers, dermatologists, or allergists use the blunt side of a pen or the tongue blade (like a tongue depressor).

Individual bumps from hives usually disappear within 24 hours. Another physical assessment involves circling one with a special pen and checking to see its progress over time.

Skin Prick Test

Some types of acute urticaria are triggered by allergic reactions. To determine if this is the case, an allergist or nurse will perform what’s called a skin prick test (also called a scratch test). This involves applying a small amount of a potential allergen on a small area of the skin and then, as the name implies, pricking or scratching it. After 15 minutes, your healthcare provider then assesses the scope and scale of your skin’s reaction.     

This test is easily administered, inexpensive, and highly effective. Most cases of hives are acute, and researchers have found allergens to be involved in 88% of acute cases.

Blood Tests

Blood tests may be another step for confirming a diagnosis of urticaria. Your healthcare provider will take your blood sample and send it to a lab for testing. Blood tests are generally indicated for chronic cases in which symptoms persist longer than six weeks.

The following blood tests can screen for inflammatory markers in the blood:

• Complete blood count (CBC): Checks for total blood cell count and plasma (the liquid component of blood), as well as the concentration of other blood components, like hemoglobin (blood protein that delivers oxygen to tissues and organs)
• Erythrocyte sedimentation rate (ESR): Determines the rate that red blood cells sink to the bottom of a tube of blood over an hour—which can be used to detect chronic inflammation
• C-reactive protein (CRP): Measures levels of CRP (a protein produced by your liver) in your blood—which can be used to detect acute inflammation
• Thyroid-stimulating hormone (TSH): Measures levels of TSH, which can indicate the status of your thyroid gland (controls hormone levels and metabolism) 

In addition, allergists or dermatologists may use a common allergy test, called an allergen-specific immunoglobin E (IgE) assay. This is a blood test that measures levels of IgE, which is an antibody, or type of protein that’s activated as part of an immune reaction that’s causing symptoms.

Testing for Urticaria Triggers

Some rarer cases of hives are triggered by exposure to certain physical stimuli, such as heat, cold, sweat, and water. This is known as inducible urticaria—also called physical urticaria. If suspected, allergists may perform challenge testing, which involves exposing parts of the body to the stimuli. Here’s a quick breakdown of these tests:

• Ice cube test: To see if you have cold urticaria, an ice pack will be placed on the skin for 10 to 15 minutes and then removed to see if symptoms arise.
• Water immersion: For those suspected of having hives triggered by water (known as aquagenic urticaria), a part of the body will be immersed in water or covered with a warm wet compress.
• Hot bath test: To screen for hives due to rising body temperature—known as heat urticaria—you’ll be asked to take a hot bath, with signs of outbreak screened for afterward.
• Pressure testing: To see if pressure or force on the skin is the trigger weight is placed on the shoulder or thigh to see if hives develop (delayed pressure urticaria).

Questionnaires on Living With Hives 

To assess the severity of your urticaria and its impact on quality of life, you may be asked to fill out a standardized questionnaire. There are several types of questionnaires, including:

• Dermatology Quality of Life Index (DQLI): A longstanding standard of assessment, the DQLI has 10 questions that seek to evaluate the quality of life impact of a wide range of dermatological (skin) conditions.
• Urticaria Severity Score (USS): The USS includes 12 questions with seven possible responses for each to assess the severity of chronic hives symptoms.
• Chronic Urticaria Quality of Life Questionnaire (CU-Q2oL): The CU-Q2oL features 23 questions related to chronic hives. It is designed to assess severity and impact across six categories: itchiness (pruritus), swelling (angioedema), impact on life activities, sleep problems, looks, and limits (limitations on activity).

Screening for Related Conditions 

The symptoms of hives can closely resemble those of many other skin conditions as well as other systemic diseases. During the diagnosis, your healthcare provider will determine whether your symptoms are from these conditions or urticaria. In particular, urticaria may resemble:

• Urticarial vasculitis: This is a type of autoimmune disease—a condition where the immune system is hyperactive and attacks healthy tissues in the body. Urticarial vasculitis causes inflammation of arteries and veins in the body, affecting blood flow to the organs and skin. 
• Urticarial bullous pemphigoid: This is an autoimmune skin condition that can cause hives, along with blisters and itchiness.
• Systemic mastocytosis: This arises when too many mast cells—which are essential for immune function—develop. It can cause hives.
• Atopic dermatitis: Commonly known as atopic eczema, or eczema, this is a chronic inflammatory skin condition characterized by scaly, dry, irritated, and dry skin.
• Allergic contact dermatitis: Also called allergic contact eczema, this is a type of eczema where skin contact with an allergen leads to an itchy rash. Common allergens include poison ivy or fragrances.
• Erythema multiforme: This is an allergic reaction on the skin in response to a medication or infection.  
• Anaphylaxis: This is a severe and dangerous allergic reaction throughout the body. It can arise as shortness of breath, swelling in the face, and other symptoms. Anaphylaxis requires immediate medical intervention.
  
• Systemic lupus erythematosus (SLE): This is the most common type of lupus—a group of autoimmune diseases that can cause inflammation in many parts of the body, including the skin. SLE can cause hives.
• Schnitzler's syndrome: This an autoimmune condition that can cause chronic urticaria, along with other symptoms like joint and bone pain.
• Muckle–Wells syndrome: This is a rare hereditary disorder that causes hearing loss alongside symptoms on the skin.

Furthermore, hives may occur at the same time as—or be comorbid with—other diseases. The most common of these are:

• Rhinovirus infections: Respiratory illness, especially the common cold, can cause hive formation. 
• Depression and anxiety: Psychological distress, anxiety, and depression can manifest as skin inflammation and trigger hives.
• Type 1 diabetes: This is an autoimmune disease in which the immune system blocks the pancreas from producing enough insulin, a hormone that processes sugars. 
• Liver diseases: These may include different types of hepatitis—like hepatitis A, B, or C—which can cause inflammation of the liver and lead to urticaria, among other symptoms. 

Generally, an assessment of your symptoms and medical history, alongside results from blood tests are enough to rule out similarly presenting diseases or identify comorbid conditions. But to confirm a diagnosis, your healthcare provider may order several other tests:

• Skin biopsy: A healthcare provider takes a small sample of your skin and sends it to a lab to rule out urticarial vasculitis (a condition characterized by inflammation of blood vessels).  
• Antibody tests: Tests for specific antibodies may help rule out autoimmune conditions. These include complete biochemistry tests and antinuclear antibody (ANA) immunofluorescence assay (IFA).
• Genetic tests: These can test to see if you have certain genes linked to genetic conditions, as some are associated with hives or can cause them.
• Liver function: Blood or urine tests of liver function, such as the bilirubin test, may also prove necessary to screen for underlying health conditions. 

A Quick Review

The diagnosis of urticaria, commonly called hives, primarily involves an assessment of medical history, as well as a physical examination of affected areas. In chronic cases, additional tests may be needed. These include allergy tests, blood tests, as well as tests to identify any triggers for urticaria. In some cases, an evaluation will also be needed to screen for other conditions that may be causing the symptoms, or those that accompany the issue.