Hives (Urticaria)

Hives are raised, itchy welts on the skin. The medical name is urticaria. A welt can be small like a fingertip or large like a plate, and welts can join together into bigger patches. Their edges are often clearly marked, and the center may turn pale when you press on it.

A key feature of hives is that each welt is temporary. An individual welt usually fades within 24 hours, often within a few hours, and leaves no mark. But new welts can keep appearing in other spots, so the rash as a whole may last longer.

Hives happen when certain cells in the skin, called mast cells, release a chemical called histamine. Histamine makes tiny blood vessels leak fluid into the skin, which causes the swelling and itch. Sometimes the swelling goes deeper and causes puffiness of the lips, eyelids, hands, or feet. This deeper swelling is called angioedema, and it often comes along with hives.

The main symptoms are welts and itch. Common signs include:

• Raised welts or bumps that can be small or large
• Itch, which can be intense; some people feel burning or stinging instead
• Welts that turn pale in the center when pressed
• Welts that change shape, move around, and fade within a day in one spot while new ones appear elsewhere

On lighter skin, welts often look pink or red. On darker skin, redness can be harder to see, so welts may look like raised skin-colored or slightly darker bumps. Some people also get deeper swelling of the lips, eyelids, hands, or feet (angioedema).

Doctors group hives mainly by how long they last and what sets them off:

• Acute urticaria: Hives that last less than six weeks. This is the most common type and is often linked to a food, medicine, or infection.
• Chronic urticaria: Hives that come and go for six weeks or longer. When no clear cause is found, it is called chronic spontaneous urticaria (an older name is chronic idiopathic urticaria).
• Physical (inducible) urticaria: Hives brought on by a physical trigger. Examples include cold, heat, sunlight, pressure on the skin, exercise, sweating, or firm stroking of the skin (dermographism). These welts usually show up within an hour of the trigger.

Hives form when mast cells in the skin release histamine and other chemicals. Histamine makes small blood vessels leak, which leads to the swelling and itch. Many different things can set this off.

Acute (short-term) hives are often linked to a clear trigger, such as:

• Foods (like nuts, shellfish, eggs, or milk)
• Medicines (like some antibiotics or pain relievers)
• Insect stings or bites
• Infections, such as a cold or other common illness

Chronic (long-term) hives are different. Often no allergy or outside cause is found, and the hives are called chronic spontaneous urticaria. In many of these cases, the immune system appears to play a role, acting against the body's own mast cells. This is not an allergy, and it does not mean something is seriously wrong. It simply means the system that makes hives is switched on more easily.

Triggers vary from person to person. Common ones include:

• Certain foods, such as nuts, shellfish, eggs, and milk
• Some medicines, including certain antibiotics and pain relievers
• Insect stings and bites
• Infections, like a cold or other viral illness
• Physical factors: cold, heat, sunlight, pressure, exercise, and sweating
• Stress

For chronic hives, a clear trigger often cannot be found. Keeping a simple diary of when hives appear can help you and your doctor spot patterns.

A doctor can usually diagnose hives by looking at the skin and hearing your story. The welts have a typical look, and the fact that each one fades quickly is a helpful clue.

For short-term hives, the cause is often clear from recent events, like a new food or medicine. Allergy testing may be used when a specific allergy is suspected.

For chronic hives, extensive testing usually is not needed, because a cause is often not found and testing rarely changes treatment. A doctor may do a few blood tests to check for related conditions, such as thyroid problems, if your history points that way. If a physical trigger is suspected, the doctor may gently test the skin, for example with cold or light pressure, to see if welts appear.

Most hives settle on their own. These steps can ease the itch and calm your skin:

• Try an antihistamine: Over-the-counter, non-drowsy antihistamines (such as cetirizine, loratadine, or fexofenadine) are the main treatment. They block histamine, which reduces the itch and welts.
• Cool the skin: A cool shower, cool compress, or calamine lotion can soothe itch.
• Wear loose clothing: Tight, scratchy fabrics can make hives worse.
• Avoid known triggers: If you can link your hives to a food, medicine, or physical trigger, steer clear of it.
• Lower heat and stress: Heat, hot showers, and stress can bring on welts in some people.

If your hives keep coming back, do not stop your daily antihistamine too soon. Taking it regularly often works better than waiting for a flare.

There is no special cream that cures hives, since the problem starts inside the skin rather than on its surface. The most useful over-the-counter option is a non-drowsy oral antihistamine. For itch relief, gentle, fragrance-free lotions, calamine, or a cool compress can help. Avoid hot water and harsh, fragranced products, which can make the itch worse.

When over-the-counter care is not enough, a doctor may suggest:

• Higher-dose antihistamines: Guidelines allow doctors to raise the dose of non-drowsy antihistamines above the standard amount for stubborn hives, under medical advice.
• Adding a second antihistamine: Sometimes a different type of antihistamine is added, such as one taken at night.
• Omalizumab: An injectable medicine for chronic hives that do not respond to antihistamines. It targets part of the immune pathway that drives hives, and it works well for many people.
• Other options: For hard-to-treat cases, medicines that calm the immune system (such as cyclosporine) may be used under close supervision.
• Short steroid course: For a severe, sudden flare, a doctor may prescribe a brief course of oral steroids. These are not used long-term.

See a doctor if hives last more than a few weeks, keep coming back, or are not controlled by over-the-counter antihistamines. A dermatologist or allergist can confirm the diagnosis and guide treatment for chronic hives.

Some symptoms need emergency care right away. Call your local emergency number if hives come with trouble breathing, wheezing, tightness in the throat, a swollen tongue or throat, dizziness or fainting, or vomiting. These can be signs of a severe allergic reaction called anaphylaxis, which is treated with an epinephrine injection (such as an EpiPen). This is uncommon, but it is important to know the warning signs.

A few conditions can look like hives:

• Eczema (atopic dermatitis): Dry, scaly, long-lasting itchy patches. Unlike hives, eczema patches do not fade within hours and often crack or flake.
• Contact dermatitis: A rash from touching an irritant or allergen. It stays where the contact happened and does not move around like hives.
• Insect bites: Individual itchy bumps that stay put for days, rather than fading within a day.
• Urticarial drug rashes and viral rashes: Some rashes from medicines or infections can mimic hives but tend to last longer in one spot.

The best clue for hives is that each welt is short-lived, moving and fading while new ones appear elsewhere.