What Causes Hives? A Dermatologist Explains Acute vs Chronic Hives, Why Food Is Rarely the Cause, and Warning Signs That Need Urgent Care

3 days ago

19 min read

Hives (urticaria) are itchy, raised red welts that appear when mast cells in the skin release histamine. Each individual welt fades on its own within 24 hours and leaves no mark. Hives lasting less than 6 weeks are called acute; hives lasting 6 weeks or longer are called chronic.

About 1 in 5 people have hives at least once in their life. Most cases clear within a few days to a few weeks. Chronic hives affect about 0.5–1% of the population and, contrary to what many people believe, are usually not caused by food allergy.

If the rash comes with swelling of the mouth, tongue or throat, trouble breathing, or feeling faint, call 1669 or go to the emergency room immediately. Do not wait to see whether an antihistamine helps.

What hives look like, and the 24-hour rule used to tell them apart

Features that point to hives rather than another rash

Raised welts or bumps (wheals): Sharp edges, from a few millimetres to large patches several centimetres across. The centre may look pale with red skin around it.
Prominent itch: More itchy than painful or burning.
They move around: One spot fades and a new one appears elsewhere within a few hours, so the rash seems to travel.
Skin returns to normal: No dark marks, bruising or scaling are left behind.

Doctors use one simple rule to tell hives from look-alike conditions: each individual spot must fade within 24 hours. Do not confuse this with the rash as a whole. A person with hives may get new welts every day for months, but if you circle one spot with a pen, that spot should be gone within a day. If the same spot lasts longer, hurts more than it itches, or leaves bruising when it fades, see a doctor, because it may be another condition.

What causes hives

When mast cells are triggered, they release histamine and other inflammatory substances. Small blood vessels widen, fluid leaks under the skin, and the skin swells into itchy welts. Mast cells can be triggered in many ways.

Infections: Especially respiratory viruses, which are common in children.
Medicines: For example NSAID painkillers, aspirin and some antibiotics.
True food allergy: Symptoms start within minutes to about 2 hours after eating and happen every time the food is eaten.
Insect stings: For example bees and wasps.
Physical triggers: Scratching, pressure, cold, heat, sweat and sunlight.
The body’s own immune system: The main mechanism behind chronic hives that have no outside trigger.

Acute urticaria: lasting less than 6 weeks

What it looks like: The rash appears suddenly, may cover the whole body, comes and goes every day, then gradually eases. Most cases improve within a few days to 2–3 weeks.

Causes: Infections, medicines, true food allergy and insect stings, although about half of cases have no trigger that can be found. If you have just started a new medicine, also consider a drug rash.

Severity and urgency: Usually not dangerous, and non-drowsy antihistamines control it. However, this type needs more attention for severe allergic reactions than the others, especially when it starts within 2 hours of eating, taking a medicine or being stung.

When to see a doctor: Go to the emergency room immediately if the mouth or throat swells, breathing is difficult or you feel faint. See a doctor the same day if you have a high fever, severe joint pain or have just started a new medicine, and see a doctor if the rash has not improved after 2–3 days of antihistamines.

Chronic spontaneous urticaria: lasting 6 weeks or longer

What it looks like: The rash appears almost every day or on and off for more than 6 weeks without a clear trigger. The itch is worst in the evening and at night. About 40% of people also have swelling of the lips or eyes. It affects women about twice as often as men.

Causes: Mostly the body’s own immune system activating mast cells, not an allergy to something outside the body. It occurs more often than average together with autoimmune thyroid disease. Stress, lack of sleep, alcohol and NSAIDs are not the root cause but can trigger flare-ups.

Severity and urgency: It does not damage internal organs and rarely causes severe allergic reactions, but it badly affects sleep and work, so it should not be left untreated.

When to see a doctor: Everyone who has had hives for more than 6 weeks should see a doctor at least once to confirm the diagnosis and plan regular daily medicine, especially if taking antihistamines every day still does not allow sleep.

Dermographism: raised lines after scratching

What it looks like: Scratching or rubbing from clothing causes red raised lines along the mark within 5–10 minutes, fading on their own within about 30 minutes.

Causes: Mast cells that are sensitive to friction. It is a common inducible type of hives, most often with no cause found, and it is usually not caused by an allergy to anything.

Severity and urgency: Not dangerous. If it does not itch, no treatment is needed. If it itches, the same non-drowsy antihistamines used for chronic hives are used.

When to see a doctor: The itch disturbs sleep, it happens every day, or you also get spontaneous welts without scratching.

Delayed pressure urticaria: bag straps, belts, soles of the feet

What it looks like: Deep, raised swelling that hurts or burns more than it itches, where pressure has lasted a long time, such as under a bag strap, at the waist under a belt, on the soles after long walking, or on the buttocks after long sitting. It usually appears late, about 3–12 hours after the pressure.

Causes: Prolonged pressure activating mast cells in the deeper layers of the skin. It often occurs together with chronic spontaneous urticaria.

Severity and urgency: Not dangerous. These welts can last longer than the 24-hour rule, even 2–3 days, and respond less well to antihistamines than other types, so the medicine often has to be adjusted by a doctor.

When to see a doctor: The pain stops you walking or working, or the welts last more than 24 hours and you are not sure pressure is the cause.

Cold urticaria: appears after cold water, air conditioning or cold items

What it looks like: Red, itchy raised areas where the skin has been exposed to cold, usually within a few minutes and most noticeable as the skin warms back up. Some people get lip swelling after a cold drink. People whose symptoms start when the weather changes often ask whether it is a weather-change rash, which needs to be told apart.

Causes: Mast cells that are sensitive to cold. Most cases have no cause found; a few follow an infection or involve abnormal proteins in the blood. Doctors test by placing an ice cube wrapped in plastic on the forearm for about 5 minutes and looking at the skin as it warms back up.

Severity and urgency: This type needs more care than people expect. Entering cold water with the whole body, such as jumping into a pool or the sea, can cause fainting or a severe allergic reaction, so do not swim alone.

When to see a doctor: Everyone whose rash appears with cold should have it confirmed, and go to the emergency room immediately if you have ever felt faint, had trouble breathing, or had tongue or throat swelling after cold water.

Sweat and heat urticaria (cholinergic urticaria)

Features: Many small bumps 1–3 mm wide with a red ring, appearing within minutes when the body gets hot, sweats, exercises, takes a warm bath, eats spicy food or is stressed. They fade within 30–90 minutes.

Causes: A rise in body temperature activates mast cells through the nerves that control sweating. It is common in teenagers and young adults. It must be told apart from sweat allergy of other kinds and from prickly heat, whose bumps last longer and do not fade within an hour.

Severity and urgency: Usually not dangerous but disrupts exercise. If you feel faint or have trouble breathing during exercise, exercise-induced anaphylaxis must be considered, which is a different condition.

When to see a doctor: You cannot do normal activities, or you have ever felt faint, had trouble breathing, or had mouth or throat swelling during exercise. Stop immediately and go to the emergency room.

Solar urticaria (sunlight)

What it looks like: Red, itchy raised areas on skin exposed to sunlight within a few minutes, usually fading within 1–2 hours after getting out of the sun.

Causes: Certain substances in the skin change form when exposed to light and then activate mast cells. It is uncommon. It must be told apart from other light-triggered rashes that appear late and last for days, including drug-induced sun rashes.

Severity and urgency: Usually more disruptive than dangerous, but people with a widespread rash may feel faint. Avoid the sun, wear long sleeves and apply broad-spectrum sunscreen.

When to see a doctor: The rash appears every time you are in the sun, antihistamines do not control it, or you have symptoms affecting the whole body.

Facial hives: rash on the cheeks and forehead

What it looks like: Red, itchy raised patches on the cheeks, forehead or neck that fade within a day like hives elsewhere. Sometimes the eyelids or lips swell as well.

Causes: The same as ordinary hives; there is no cause specific to the face. If a rash stays in the same place for several days, or is red and peeling after changing cosmetics, it is more likely contact dermatitis than hives.

Severity and urgency: A rash on the face alone is no more dangerous than elsewhere. What matters is whether the mouth, tongue or throat is swelling. Do not apply steroid cream to the face yourself, because it does not help hives and thins the skin if used for long.

When to see a doctor: Go to the emergency room immediately if the tongue or throat swells, your voice changes or breathing is difficult, and see a doctor if a facial rash stays in the same place for more than 24 hours.

Swollen lips and eyes (angioedema): deep swelling with hives or on its own

What it looks like: Swelling in the deeper layers of the skin at the lips, eyelids, hands, feet or genitals. It feels tight or dully painful rather than itchy and usually lasts 1–3 days. If only the lips swell without a rash, also read swollen lips: which types are dangerous.

Causes: If hives are present, it is usually the same histamine mechanism. If swelling occurs with no rash at all, a bradykinin mechanism must be considered, for example ACE inhibitor blood pressure medicines (enalapril, lisinopril) or hereditary angioedema.

Severity and urgency: Swelling of the tongue or throat is immediately dangerous. The bradykinin type does not respond to antihistamines and steroids, so do not assume it will improve after taking them.

When to see a doctor: Go to the emergency room immediately if the tongue or throat swells, swallowing is difficult or your voice becomes hoarse. If you get occasional swelling without a rash, take a blood pressure medicine, or have family members with similar swelling, see a doctor for assessment. Do not stop blood pressure medicine yourself before talking to a doctor.

Hives at night: why the itch is worst at bedtime

What it looks like: The rash and itch are worst from evening into the night, you wake up itching in the middle of the night, and by morning the rash has almost gone. This is common in chronic hives.

Causes: The hormone cortisol, which helps control inflammation, is low at night; the body warms up under the blanket, waistbands press on the skin, and nothing distracts from the itch. If the itch is at night but the bumps last for several days, especially between the fingers and on the wrists, or others at home are itching too, think of scabies first, and red bumps like mosquito bites that stay in the same place are not hives either.

Severity and urgency: Not dangerous by itself, but poor sleep keeps the rash flaring, so it should be treated seriously. If the itch is not limited to clear welts, see other causes in itching all over at night.

When to see a doctor: Waking in the night from itching more than two or three nights a week; a doctor can adjust the timing and dose of medicine. If you wake with a swollen mouth, a tight throat or trouble breathing, go to the emergency room immediately.

Hives in children

What it looks like: Red raised welts that come and go like in adults. Young children may not say they itch but are fussy and scratch. Some have rings with a darker centre, which can frighten parents.

Causes: Mostly acute hives following a viral infection, then medicines and true food allergy, especially in young children, such as milk, egg and peanut. A child with hives and a cold does not always have an allergy to the medicine or food taken at that time.

Severity and urgency: Most cases clear on their own within 1–3 weeks. Non-drowsy liquid antihistamines can be used from about 2 years of age, with the dose calculated by a doctor from age and weight. Do not split an adult dose for a child yourself.

When to see a doctor: Go to the emergency room immediately if the mouth or throat swells, breathing is difficult, there is repeated vomiting after eating, or the child is drowsy. See a doctor if a baby under 1 year has a rash, if there is a high fever, if joint pain or swelling stops the child walking, or if it lasts more than 6 weeks.

Hives with trouble breathing: severe allergic reaction (anaphylaxis)

What it looks like: Hives appearing quickly all over the body within minutes to about 2 hours of a trigger, together with any one of these symptoms in another body system.

Swelling of the mouth, tongue or throat, a tight throat, hoarse voice, difficulty swallowing
Difficulty breathing, wheezing, chest tightness
Faintness, dizziness, palpitations, collapse, low blood pressure
Severe cramping abdominal pain, repeated vomiting or diarrhoea after a trigger

Causes: Food allergy, medicines, especially antibiotics and NSAIDs, and insect stings.

Severity and urgency: A life-threatening emergency. The main medicine is adrenaline (epinephrine), injected into the muscle of the outer thigh; the adult dose is 0.3–0.5 mg. Antihistamines and steroids are not the main treatment and must not replace it. Even after symptoms improve, observation for generally 4–6 hours is needed because symptoms can return.

When to see a doctor: Call 1669 immediately. Do not drive yourself. Lie flat with legs raised if you feel faint; sit up if breathing is difficult. If you carry an adrenaline auto-injector, use it immediately. Afterwards everyone should see a doctor to find the cause and plan prevention for next time.

Rashes that look like hives but are not

Urticarial vasculitis: The same spot lasts more than 24 hours, burns or hurts, and leaves bruising or dark marks when it fades. There may be fever and joint pain. A skin biopsy and blood tests are needed.
Erythema multiforme: Rings within rings like a target that last several days, often following cold sores, sometimes with mouth sores.
Drug rash: Small red spots spread on both sides that last several days. If there is fever, sores in the mouth or eyes, or peeling skin, see a doctor urgently, because it may be a severe drug rash such as SJS.
Insect bites and bite reactions: Bumps stay in the same place for days, with a bite mark in the centre.
Infection rashes: If an itchy red rash all over the body comes with fever and lasts several days, a doctor should check whether it is another illness.

If you have hives, what should you not eat, and what do you really need to avoid

The evidence-based answer is that most hives have no list of forbidden foods. What to avoid depends on the type of hives.

If it is a true food allergy: Avoid only the specific food that brings on the rash every time within about 2 hours, such as shrimp, peanuts or egg, and have it confirmed by a doctor. If you have ever had a severe reaction, avoid it strictly.
If it is chronic hives: Long lists of foods to avoid, such as seafood, pickled foods, chicken or so-called triggering foods, usually do not help and make quality of life worse.
NSAID painkillers and aspirin: For example ibuprofen and diclofenac make chronic hives flare in about 20–30% of people. If you need a painkiller, paracetamol is usually safer. But if a doctor has prescribed aspirin for a heart condition, do not stop it yourself before talking to the doctor.
Alcohol: It widens blood vessels, so the rash and itch usually get worse straight away.
Spicy, hot food: It is not the cause, but it warms the body and can trigger the sweat and heat type.
High-histamine foods or foods with additives: The evidence is limited. A doctor may in some cases try avoiding them for a short period of 2–3 weeks, and you should stop avoiding them if there is no improvement.

If you suspect a particular food, write down the time you ate it and the time the rash appeared. If it does not happen every time, that food is usually not the cause.

Basic home care for hives

Apply a cold compress to itchy areas for 10–15 minutes at a time, except for people with cold urticaria.
Stay in a cool room, wear loose, light clothing, avoid hot showers and do not scratch.
Take a non-drowsy antihistamine at the dose on the label or as advised by a pharmacist. See how to choose in which itch medicine and antihistamine to take.
Calamine lotion can be used for a cooling effect, but steroid creams do not help hives.
Do not use rubbing alcohol, medicated balm or herbal remedies on the skin, because they may irritate it further.
Do not buy packet medicines with unknown ingredients, because they may contain hidden steroids.

If the rash has not improved after 2–3 days, or there are the danger signs above, do not keep waiting.

Medicines for hives: 4 steps from international guidelines

The goal is no rash and no itch, using medicines that are safe in the long term, then reducing them once the condition settles. Doctors assess the response at every step with the UAS7 symptom score, which ranges from 0 to 42; a value of 6 or below means good control. The details below are information to help you understand the treatment plan. Choosing and prescribing medicines is the responsibility of the examining doctor.

Step 1: non-drowsy antihistamine, once a day

Usual adult doses

Cetirizine 10 mg: acts quickly; some people feel slightly drowsy.
Levocetirizine 5 mg: similar to cetirizine.
Loratadine 10 mg: little drowsiness.
Desloratadine 5 mg: little drowsiness.
Fexofenadine 180 mg: little drowsiness; do not take with fruit juice.
Bilastine 20 mg: take on an empty stomach, 1 hour before or 2 hours after a meal, and not with fruit juice.

How long: For acute hives, take it every day until the rash stops appearing and for several days more, usually no more than 1–3 weeks in total. For chronic hives, take it every day, even on days with no rash, not only when it itches.

What decides whether it works: Assess at 2–4 weeks, or sooner if you cannot tolerate the symptoms. If UAS7 is still above 6, move up a step. People with kidney disease need a lower dose of cetirizine and levocetirizine.

Step 2: increase the same antihistamine up to 4 times, under a doctor’s supervision

A doctor may increase to 2–4 times the usual dose, for example cetirizine 10 mg, 2–4 tablets a day. Guidelines recommend increasing the same medicine rather than using several at once. Do not start doses above the label yourself.

How long: Try one dose for about 2–4 weeks. If it works, continue; once control has lasted about 3 months, the doctor will reduce it gradually.

What decides whether it works: Many people who did not respond to the usual dose improve at this step. If it is still not controlled at 4 times the dose, move to the next step; do not keep switching medicines back and forth.

Step 3: omalizumab injection

A biologic injection that binds IgE. The standard dose is 300 mg, injected under the skin every 4 weeks, used in people aged 12 years and over whose symptoms cannot be controlled with high-dose antihistamines.

How long: Some people improve within 1–4 weeks, others more slowly. Doctors often allow up to 6 months to assess, then gradually reduce the frequency once controlled.

What decides whether it works: In the main studies, about 52–66% achieved good control (UAS7 of 6 or below) at 12 weeks. Side effects include pain at the injection site and headache. Severe allergic reactions are uncommon, but you must be observed after the injection.

Step 4: cyclosporine

An oral immunosuppressant, at no more than 5 mg per kilogram of body weight per day, taken together with an antihistamine. It is used in people who do not respond to omalizumab or cannot use the injection.

How long: Usually used for a limited period of about 3–6 months.

What decides whether it works: Both symptoms and safety must be considered. The doctor will monitor blood pressure and kidney function regularly and stop the medicine if the results are abnormal.

Newer medicines approved for chronic hives in some countries include dupilumab and remibrutinib. Access differs from country to country, and a doctor can tell you whether they suit your case.

Oral steroids: short use only, for severe flare-ups

Prednisolone tablets, usual dose 0.5–1 mg per kilogram of body weight per day for 3–7 days, used only when the rash is severe or there is a lot of swelling. It works quickly but is not a medicine to control chronic hives. Repeated courses or regular steroid injections risk high blood sugar, high blood pressure, thinning bones, and the rash returning when stopped.

Medicines that should not be the mainstay

Older drowsy antihistamines such as chlorpheniramine are not suitable as a long-term main medicine, because they impair sleep and concentration and the effect lingers into the next day. Creams and ointments do not help hives.

If antihistamines do not work, what to do next

About half of people with chronic hives cannot be controlled with the usual dose of antihistamine. This is common, and there are further steps. The steps a doctor takes are:

Check how the medicine is taken: Is it taken every day, at the right time, with fruit juice or not, and has the high dose been tried under a doctor.
Confirm it is really hives: If the same spot lasts more than 24 hours or leaves bruising, the doctor will consider a skin biopsy.
Look for triggers that are still present: NSAIDs, alcohol, lack of sleep, pressure, cold or heat, and challenge tests if suspected, such as skin stroking or placing ice.
Blood tests only as needed: A full blood count with differential, an inflammation marker (ESR or CRP), thyroid antibodies (anti-TPO) and total IgE. Other tests are done when symptoms suggest them.
Record the UAS7 symptom score: Note the number of welts and the level of itch once a day for 7 days, to see whether each change in medicine really works.
Step up the treatment: From the usual dose to up to 4 times the dose for 2–4 weeks, then omalizumab, and then cyclosporine.

What usually does not help is broad food allergy panel testing, especially IgG testing for foods, because a positive result does not mean a true allergy and leads to unnecessary food avoidance.

Hives during pregnancy and breastfeeding

Hives can flare or start for the first time during pregnancy. The medicines doctors usually choose are loratadine 10 mg or cetirizine 10 mg, which have more safety data than other medicines. Raising the dose or using advanced medicines needs discussion with both a dermatologist and an obstetrician. Pregnant or breastfeeding women should not start medicines themselves, and should see a doctor when a rash first appears in pregnancy, because it needs to be told apart from rashes specific to pregnancy.

How many days do hives last

Acute hives: Most improve within a few days and clear within 2–3 weeks.
Chronic spontaneous hives: About 30–50% settle within 1 year and more than half settle within 5 years, while a minority last longer. People with severe symptoms or with lip swelling tend to have it longer.
Inducible hives: Often last several years but can be controlled by avoiding the trigger together with medicine.

While waiting for the condition to settle, the aim is to live normally. Taking a non-drowsy antihistamine continuously for months does not make it stop working or cause addiction.

When to see a dermatologist

Book a dermatologist when the rash lasts more than 6 weeks, daily antihistamines still disturb sleep or work, the same spot lasts more than 24 hours and leaves marks, there is repeated swelling of the mouth or eyes, or you suspect you have the type triggered by cold or exercise.

Quick summary

Hives are itchy raised welts where each individual spot fades within 24 hours. If the same spot lasts longer or leaves bruising, a doctor must examine it.
The dividing line is 6 weeks: acute hives usually come from infection, medicines or food, while chronic hives are usually not a food allergy.
Inducible hives are classified by scratching, pressure, cold, sweat and heat, or sunlight.
The first medicine is a non-drowsy antihistamine once a day. If it does not control hives in 2–4 weeks, a doctor can raise it up to 4 times, then consider omalizumab.
Most people do not need a long list of forbidden foods, but should avoid NSAIDs and alcohol.
If the mouth, tongue or throat swells, breathing is difficult or you feel faint, call 1669 immediately.

Frequently asked questions about hives

How do you treat hives, and how can they fade quickly

What works is a non-drowsy antihistamine at the dose on the label, for example cetirizine 10 mg or loratadine 10 mg once a day, together with a cold compress for 10–15 minutes at a time, staying in a cool room, wearing loose clothing, and avoiding hot showers and alcohol. The medicine starts to work within about 1–3 hours. Steroid cream or medicated balm does not make the rash fade. If it has not improved after 2–3 days, see a doctor, and if the mouth or throat swells or breathing is difficult, go to the emergency room immediately without waiting for the medicine to work.

What causes hives at night

Hives are often itchiest at night because cortisol, which helps control inflammation, is low, the body warms up under the blanket, waistbands press on the skin, and nothing distracts from the itch. This pattern is common in chronic hives. Sleep in a cool room, wear loose clothing, and talk to a doctor about taking an antihistamine every evening. But if the itch is at night and the bumps stay in the same place for several days, especially between the fingers, or others at home are itching too, it may be scabies, not hives. If you wake with a swollen mouth or trouble breathing, go to the emergency room immediately.

Are facial hives dangerous

A raised rash on the cheeks or forehead alone is no more dangerous than a rash on the arms or legs, and it usually fades within a day. What matters is whether the lips, tongue or throat are swelling. If your voice changes, swallowing is difficult or breathing is not comfortable, go to the emergency room immediately. Mild swelling of the eyelids or lips with normal breathing comes from swelling in the deeper skin and usually clears in 1–3 days, but see a doctor if it keeps coming back. Do not apply steroid cream to the face yourself, because it does not help hives and harms the skin if used for long.

What do hives look like

Hives look like raised red or pale patches with sharp edges and a strong itch, and can appear on any part of the body. Each spot fades within 24 hours and then a new one appears elsewhere, and once it fades the skin returns to normal with no dark marks or scaling. Some people also have swelling of the mouth or eyes. If a rash stays in the same place for more than 24 hours, hurts more than it itches or leaves bruising, it may be another condition. If the rash comes with a tight throat, trouble breathing, vomiting or faintness, it may be a severe allergic reaction needing immediate emergency treatment.

What are the causes of hives

The cause depends on how long they last. Hives lasting less than 6 weeks usually come from a viral infection, medicines such as antibiotics and NSAIDs, true food allergy or insect stings, but about half have no trigger that can be found. Hives lasting 6 weeks or more are usually related to the body’s own immune system and are not caused by food allergy. Another group is caused by scratching, pressure, cold, sweat and heat, or sunlight. Stress and lack of sleep are not the cause but can make the rash flare.

If you have hives, what should you not eat

There is no list of forbidden foods that applies to everyone. Avoid only the food that brings on the rash every time within about 2 hours after eating. Most chronic hives are not caused by food, so blanket avoidance of seafood, pickled foods or so-called triggering foods usually does not help. What you really should avoid is alcohol and NSAID painkillers such as ibuprofen, as well as aspirin, which can make the rash flare. If you must take aspirin as prescribed by a doctor, do not stop it yourself; talk to the doctor first.

The information in this article is general knowledge, not a diagnosis or an individual treatment order. Treatment results vary from person to person. The doses mentioned are usual adult doses. Choosing and prescribing medicines is the responsibility of the examining doctor.

Written by Dr. Patara Voravutinon, Dermatologist · Last reviewed November 4, 2026