Urticaria is the medical term for hives, the itchy, raised welts that appear on the skin when cells in your body release histamine and other inflammatory chemicals. About 20% of people worldwide will experience urticaria at some point in their lives, making it one of the most common skin conditions. It can be a one-time reaction to something you ate or touched, or it can recur for months or even years with no obvious cause.
What Hives Look and Feel Like
The hallmark of urticaria is the wheal: a smooth, raised area of swelling on the skin that ranges from a few millimeters to several centimeters across. Wheals can be round or take on irregular, map-like shapes. They typically start out red, then develop a pale center surrounded by a red border, creating what doctors call a “wheal and flare” pattern. The distribution is usually asymmetrical, popping up in different spots across the body rather than following a neat pattern.
Itching is the defining symptom. It can range from mildly annoying to intense enough to interfere with sleep and daily life. Individual wheals fade within 24 hours without leaving any mark, bruise, or scar on the skin. But new ones often appear in different locations as old ones resolve, which can make it feel like the rash is moving around your body.
Angioedema: Deeper Swelling
Some people with urticaria also develop angioedema, which is swelling that occurs deeper beneath the skin’s surface. Rather than raised, itchy welts, angioedema shows up as soft, puffy swelling, most commonly around the eyes, lips, and mouth. It tends to feel more like burning or pressure than itching. Angioedema can occur alongside hives or on its own, and it usually resolves within one to three days.
What Happens Inside Your Skin
Urticaria starts with mast cells, a type of immune cell stationed throughout your skin. When something triggers these cells, they release stored histamine along with other inflammatory chemicals. The histamine acts on tiny blood vessels, making them leak fluid into the surrounding tissue. That fluid buildup is what creates the raised welt you see on the surface. At the same time, histamine stimulates nerve endings in the skin, sending itch signals to your brain.
The trigger for mast cell activation varies. In allergic urticaria, the immune system recognizes a specific substance (a food protein, a medication, an insect venom) and produces antibodies that latch onto mast cells. The next time that substance enters your body, it cross-links those antibodies and the mast cell dumps its contents. But mast cells can also be activated through non-allergic pathways, including pressure, temperature changes, and autoimmune processes where the body’s own antibodies mistakenly target the mast cells themselves.
Acute vs. Chronic Urticaria
The six-week mark is the dividing line. Acute urticaria lasts fewer than six weeks. Chronic urticaria persists for six weeks or longer, with recurring episodes of hives or swelling. The two forms differ not just in duration but often in their underlying causes and how they respond to treatment.
Acute urticaria is far more common and usually has an identifiable trigger. It often resolves on its own once the trigger is removed. Chronic urticaria affects roughly 0.8% of the global population at any given time, and in many cases, no external trigger can be found. This form is called chronic spontaneous urticaria.
Common Triggers for Acute Hives
The list of potential triggers is long, but certain categories come up repeatedly:
- Infections: Viral upper respiratory infections are among the most common triggers, particularly in children. A simple cold can set off hives that last days to weeks.
- Medications: Antibiotics (especially penicillin-type drugs) and anti-inflammatory painkillers are frequent culprits.
- Foods: Nuts, eggs, fish, shellfish, and mushrooms are well-known food triggers. The reaction typically appears within minutes to a couple of hours after eating.
- Environmental allergens: Pollen, mold spores, dust mites, and animal dander can cause hives in sensitized individuals.
- Contact triggers: Chemicals, cosmetics, certain plants, and latex can produce hives at the exact site of skin contact.
Why Chronic Hives Often Have No Clear Cause
Chronic spontaneous urticaria is frustrating precisely because it seems to come from nowhere. You can eat the same foods, use the same products, and follow the same routines, yet hives keep appearing. Research over the past two decades has pointed increasingly toward autoimmune mechanisms. Up to 50% of people with chronic spontaneous urticaria show evidence of autoimmune activity, where the body produces antibodies that attack its own mast cells or the antibodies sitting on their surface.
One well-studied pathway involves antibodies that target thyroid proteins. Thyroid peroxidase, a protein normally found in the thyroid gland, can enter the bloodstream and bind to mast cells. The immune system then attacks these cells as if they were foreign invaders, triggering histamine release. This is why thyroid conditions are more common in people with chronic hives than in the general population. The term “autoallergy” has been used to describe this process, where your immune system essentially becomes allergic to components of your own body.
Physical Urticaria: Hives From Touch and Temperature
Some people develop hives in response to specific physical stimuli. These are called inducible urticarias, and each subtype has a distinct trigger:
- Dermatographism: Hives that appear where the skin has been scratched, rubbed, or pressed. You can literally “write” on the skin and watch raised letters appear. This is the most common form of physical urticaria.
- Cold urticaria: Hives that develop within minutes of contact with cold air, cold water, or cold objects. Swimming in cold water can be particularly dangerous because the widespread skin exposure can trigger a severe reaction.
- Delayed pressure urticaria: Deep, sometimes painful swelling that appears hours after sustained pressure, such as from a waistband, a tool handle, or sitting on a hard surface.
- Solar urticaria: Hives triggered by sunlight exposure.
- Vibratory urticaria: Hives caused by vibration, such as from using power tools or riding a motorcycle.
Cholinergic urticaria is a related but distinct condition. Rather than being triggered by something touching the skin, it’s triggered by a rise in core body temperature. Exercise, hot baths, stress, or even spicy food can set it off. The hives tend to be smaller (pinpoint-sized) and widespread, often appearing on the chest and arms first.
How Urticaria Is Treated
Antihistamines are the foundation of treatment. The newer, non-drowsy type taken once daily is the standard first step. If a standard dose doesn’t control the hives, the dose can be increased to up to four times the usual amount, which is safe for most people and effective in a significant number of cases.
For chronic spontaneous urticaria that doesn’t respond to antihistamines even at higher doses, a biologic injection that blocks the antibody involved in mast cell activation is the next option. It was the first drug specifically approved for chronic hives that resist antihistamine treatment and is available for adults and adolescents 12 and older. It works by reducing the number of antibodies available to trigger mast cells, lowering the overall reactivity of the immune system in the skin.
For acute urticaria with a known trigger, the most effective treatment is avoidance. If a specific food, medication, or environmental exposure is responsible, eliminating it often resolves the problem entirely. Short courses of oral corticosteroids are sometimes used for severe acute flares but aren’t appropriate for long-term management of chronic hives.
When Hives Signal Something Else
Most urticaria is uncomfortable but not dangerous. However, certain features suggest a different or more serious condition. If individual hives last longer than 24 to 48 hours and leave behind bruising or skin discoloration, the cause may be urticarial vasculitis rather than ordinary hives. This condition involves inflammation of blood vessels in the skin and is often accompanied by joint pain, fever, or unexplained weight loss. A skin biopsy can confirm the diagnosis.
Angioedema without any hives, especially if it runs in families, can indicate hereditary angioedema, a genetic condition involving a deficiency in a specific blood protein. Unlike ordinary angioedema, this form commonly causes abdominal pain and can involve dangerous swelling of the airway. Episodes typically last two to three days and don’t respond to standard antihistamines.