hives blood test explained

Overview

Hives are raised, red or skin-coloured bumps on the skin that are often itchy. They can appear suddenly and fade within hours or days. A blood test for hives is a simple blood draw that helps find the cause, especially when hives keep coming back (chronic hives).

Yes, hives are very common. However, the need for a blood test is less common – most people with short-lived hives do not need one.

Anyone can get hives – children, adults, and older adults. Women are slightly more likely to have chronic hives. People with a history of allergies, autoimmune diseases (like thyroid problems), or those who have had a recent infection may be more likely to need a blood test.

Symptoms

Common symptoms

• Raised, red or skin-coloured welts (bumps) that can be small or large
• Intense itching, sometimes burning or stinging
• Welts that change shape, move to different parts of the body, or come and go within hours

Symptoms in children

• Same raised, itchy welts as adults
• Children may also have swelling around the eyes, lips, or genitals (angioedema)
• They can be more irritable due to itching

Symptoms in older adults

• Hives can last longer and may be linked to medications they take
• Skin may be more fragile, so scratching can cause bruising or infection
• Older adults may also have other health conditions that complicate diagnosis

Causes

Main causes

• Allergic reactions to food, medicine, insect stings, or latex
• Infections – especially viral illnesses like colds or COVID-19
• Autoimmune conditions – your immune system attacks your own body (e.g., thyroid disease)
• Physical triggers – pressure, cold, heat, sun, exercise, or water (called physical urticaria)
• Stress – emotional stress can trigger or worsen hives in some people
• Chronic idiopathic urticaria – meaning the cause is unknown, even after tests

Risk factors

• Having a history of allergies, asthma, or eczema
• Taking certain medications (like NSAIDs or antibiotics)
• Having an autoimmune disease (like lupus or thyroiditis)
• Recent infection or vaccination
• Being a woman (chronic hives more common in women)

When to see a doctor

See a doctor urgently if:

• If you have hives along with swelling of the lips, tongue, or throat, or any trouble breathing – call your local emergency number immediately.
• If hives appear after starting a new medicine, seek same-day medical advice.

Book a routine appointment if:

• If hives keep coming back for more than 6 weeks (chronic hives), see your GP for a blood test.
• If hives are so itchy they interfere with sleep or daily life.
• If you have other symptoms like fever, joint pain, or weight loss.

Diagnosis

Your doctor will first ask about your symptoms and examine your skin. They may ask about triggers, recent illnesses, medicines, and your health history. If your hives are chronic or severe, they may recommend a blood test to look for an underlying cause.

Tests that may be done

• Complete blood count (CBC) – to check for signs of infection or other problems.
• Erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) – to look for inflammation.
• Thyroid function tests – to see if an underactive or overactive thyroid is causing hives.
• Allergy tests – sometimes done as blood tests (specific IgE) to check for common allergens, though this is not routine for chronic hives.
• Antinuclear antibody (ANA) test – to screen for autoimmune conditions like lupus.
• Other tests if specific causes are suspected (e.g., tests for Helicobacter pylori infection or blood cell abnormalities).

What to expect at your appointment

A blood test is quick. A nurse or phlebotomist will take a small sample from a vein in your arm. You may feel a brief pinch. Results usually take a few days to a week. Your doctor will discuss what the results mean and whether further tests or treatment are needed.

Treatment

Treatment for hives focuses on relieving symptoms and, if possible, addressing the underlying cause. Most cases of acute hives get better on their own. For chronic hives, treatment aims to control symptoms and improve quality of life. Your doctor will create a plan that's right for you.

Self-care at home

• Avoid known triggers (e.g., certain foods, heat, pressure, tight clothing).
• Apply a cool, damp cloth to the itchy areas or take a cool bath.
• Wear loose, soft clothing made of cotton.
• Avoid hot showers, vigorous exercise, and scratching (it makes hives worse).
• Keep a diary of when hives occur to help identify triggers.

Medical treatments

Doctors usually recommend antihistamines – these are medicines that block histamine, the chemical that causes hives. Antihistamines can be taken as pills, liquids, or applied to the skin as creams. Some types cause drowsiness; others are non-drowsy. For severe or chronic hives that don't respond to antihistamines, doctors may consider other treatments such as certain prescription tablets or injections that target the immune system. Always follow your doctor's advice on which treatment is best for you.

When is surgery considered?

Surgery is not used to treat hives. In very rare cases, if an underlying condition like a thyroid nodule is found that might be causing hives, surgery for that condition could be considered – but only after thorough discussion with specialists.

Living with this condition

Living with chronic hives can be frustrating, but most people find relief with treatment. Keep antihistamines on hand if needed. Learn your triggers and avoid them. Wear soft fabrics and keep your home cool. If you have a pet you are allergic to, limit exposure.

Lifestyle tips

• Manage stress through relaxation techniques like deep breathing, meditation, or gentle exercise.
• Avoid alcohol and extremely spicy foods, as they can worsen hives in some people.
• Stay hydrated and use fragrance-free moisturizers to soothe skin.
• Get enough sleep – fatigue can make hives worse.

Diet and exercise

There is no specific diet for hives. However, if you notice certain foods (like shellfish, nuts, eggs, or food additives) trigger hives, avoid them. Keep a food diary. Gentle exercise like walking or swimming is fine. Intense exercise that makes you hot can trigger hives in some people – if so, cool down gradually and stay hydrated.

Mental health and emotional wellbeing

Chronic hives can be stressful and embarrassing. Itching can disrupt sleep, work, and social life. It's normal to feel anxious, frustrated, or down. Talk to your doctor if hives are affecting your mood – they can offer support or refer you to a counsellor.

Prevention

It's not always possible to prevent hives, especially if the cause is unknown. But you can reduce your risk by avoiding known triggers. If you have allergies, strictly avoid those allergens. If hives are caused by physical triggers (like pressure or cold), try to avoid those situations.

Vaccines

Vaccines do not prevent hives. However, getting recommended vaccines (like the flu shot or COVID-19 vaccine) can help prevent infections that might trigger hives. Rarely, some people get hives shortly after a vaccination – usually mild and temporary. Discuss any concerns with your doctor.

Screening programmes

There is no routine screening for hives. If you have a condition that increases your risk (like an autoimmune disease), your doctor may monitor you more closely. If you develop chronic hives, a blood test can screen for hidden causes.

Complications

If left untreated

• Severe itch can lead to skin damage from scratching (scratches, infections).
• Chronic hives can interfere with sleep, work, and quality of life.
• In rare cases, hives can be part of a severe allergic reaction (anaphylaxis) – this is a medical emergency.

Long-term outlook

The outlook for hives is very good. Most acute hives resolve within days. Chronic hives often improve over months or years – many people get better on their own. With proper diagnosis and treatment, symptoms can be controlled, and you can live a full, active life.

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