Hives (Urticaria)
Itchy raised welts that come and go on the skin
Quick Facts
- Type: Skin reaction (urticaria)
- Key feature: Itchy raised welts that move and fade
- Common triggers: Allergies, infections, medications
- Emergency sign: Throat or tongue swelling, trouble breathing
Overview
Hives, known medically as urticaria, are raised, itchy welts that appear on the skin. They can be small or large, may join together into bigger patches, and often have a pale center with a red or flushed border. A typical feature is that individual welts come and go, usually fading within a few hours while new ones appear elsewhere.
Hives occur when cells in the skin release histamine and other chemicals, causing small blood vessels to leak fluid into the surrounding tissue. Most cases are short-lived (acute) and harmless, but hives are occasionally part of a severe allergic reaction that needs emergency care.
Symptoms
The main features of hives are:
- Raised welts (wheals) ranging from a few millimeters to several centimeters
- Itching, which can be intense
- Welts that blanch (turn pale) when pressed
- Welts that appear and disappear, with each spot lasting less than a day
Sometimes deeper swelling called angioedema occurs, affecting the lips, eyelids, hands, feet, or genitals. Swelling of the tongue, throat, or lips with difficulty breathing or swallowing is a medical emergency and may signal a severe allergic reaction (anaphylaxis).
Causes
Hives have many possible triggers, though the cause is often not identified, especially in chronic cases. Common triggers include:
- Allergic reactions: Foods (such as nuts, shellfish, eggs), medications, insect stings, or latex
- Infections: Viral illnesses are a frequent cause, particularly in children
- Physical triggers: Pressure, cold, heat, sunlight, exercise, or scratching
- Other factors: Stress, and in chronic cases, an overactive immune response
When hives last more than six weeks (chronic urticaria), an exact trigger is often never found.
Risk Factors
- A personal or family history of allergies, hay fever, or asthma
- Recent infection or illness
- Use of certain medications
- Known food or insect-sting allergies
- Some autoimmune or thyroid conditions, especially with chronic hives
Diagnosis
Hives are usually diagnosed by their appearance and the story of how they come and go. A doctor will ask about recent foods, medications, infections, stings, and physical triggers. Most acute cases need no testing.
For chronic or recurrent hives, a doctor may suggest allergy testing or blood tests to look for underlying causes such as thyroid or autoimmune conditions, though a specific cause is often not found.
Treatment
Treatment focuses on relieving itching and avoiding triggers:
- Antihistamines: The mainstay of treatment; non-drowsy second-generation antihistamines are usually preferred and may be taken regularly for chronic hives.
- Avoiding triggers: Removing a known food, medication, or physical trigger when identified.
- Cool compresses and loose clothing: Help soothe itching.
- Stronger treatments: For severe or persistent hives, a doctor may add other medications.
A severe allergic reaction with throat swelling or trouble breathing is treated as an emergency with epinephrine and immediate medical care.
Prevention
- Identify and avoid known triggers such as specific foods, medications, or insect stings
- Keep a diary to help spot patterns with chronic hives
- Dress for temperature if cold, heat, or sweating triggers your hives
- Manage stress, which can worsen symptoms for some people
- Carry prescribed emergency medication (such as an epinephrine auto-injector) if you have a known severe allergy
When to See a Doctor
See a doctor if hives last more than a few days, keep coming back, or do not improve with over-the-counter antihistamines. Persistent hives lasting more than six weeks should be evaluated.
Call emergency services immediately if hives occur with swelling of the lips, tongue, or throat, trouble breathing or swallowing, dizziness, or a feeling of throat tightness. These can be signs of anaphylaxis, a life-threatening allergic reaction.
Frequently Asked Questions
How long do hives usually last?
Individual welts typically fade within a few hours, and most acute outbreaks clear within a day to a few weeks. When hives persist or recur for more than six weeks, they are called chronic and should be evaluated by a doctor.
What is the most common cause of hives?
Acute hives are often triggered by allergic reactions to foods, medications, or insect stings, or by viral infections. In chronic hives, a specific cause is frequently never identified.
When are hives an emergency?
Hives become an emergency when they occur with swelling of the lips, tongue, or throat, trouble breathing or swallowing, or dizziness. These can signal anaphylaxis, a severe allergic reaction that requires calling emergency services right away.
What is the best treatment for hives?
Non-drowsy antihistamines are the main treatment and relieve itching and welts. Avoiding known triggers, cool compresses, and loose clothing also help. Severe or persistent cases may need stronger medication from a doctor.
Are hives contagious?
No. Hives themselves are not contagious. However, an infection that triggers them, such as a virus, may be passed to others, even though it does not necessarily cause hives in them.
References
- Mayo Clinic. Hives and angioedema — Symptoms and causes.
- American Academy of Allergy, Asthma & Immunology (AAAAI).
- MedlinePlus, U.S. National Library of Medicine. Hives.
- American Academy of Dermatology Association.