Hives

Hives, also called urticaria, are raised, swollen welts on the skin. They may look pink, red, or close to your usual skin colour. The welts often itch, sting, or burn.

A single welt usually fades within 24 hours, but new ones may appear elsewhere. This can make the rash seem to move around the body. Hives may cover a small area or spread widely.

Acute hives last for less than six weeks. They may follow an infection, medicine, food, insect sting, or another trigger, although the cause is not always found.

Chronic hives happen on most days for six weeks or longer. In many cases, they are not caused by a specific allergy. The immune system may be activating skin cells without a clear outside trigger.

Some people also develop angioedema, which is deeper swelling beneath the skin. It commonly affects the lips, eyelids, hands, feet, or genitals. Swelling of the tongue or throat needs emergency attention because it can interfere with breathing.

Hives can appear anywhere on the body. Their size and shape may change quickly.

Common features include:

• Raised welts with clear or irregular edges
• Itching, burning, or stinging
• Welts that become pale when pressed
• Spots that fade within 24 hours and reappear elsewhere
• Deeper swelling around the eyes, lips, hands, or feet

On darker skin, redness may be difficult to see. The affected areas may look lighter, darker, or similar to the surrounding skin. The raised texture and itching may be more noticeable than a colour change.

Hives caused by pressure, cold, heat, exercise, or scratching may develop mainly where that trigger touched the skin. For example, tight clothing may cause lines of swelling, while scratching may produce raised marks.

A rash that stays in exactly the same place for more than 24 hours, is painful rather than itchy, leaves bruising, or causes skin peeling is not typical of ordinary hives. It should be medically assessed.

Hives develop when immune cells in the skin, called mast cells, release histamine and other chemicals. These chemicals cause nearby blood vessels to leak fluid, producing swelling and itching.

Acute hives can be associated with:

• Viral or bacterial infections
• Foods, particularly when symptoms begin soon after eating
• Medicines, including antibiotics and some pain relievers
• Insect stings or bites
• Contact with latex or another allergen

An allergen is a substance that the immune system mistakenly treats as harmful. When an allergy causes hives, symptoms often begin within minutes to a few hours of exposure. Hives alone do not prove that you have an allergy.

Physical triggers can also cause hives. These include cold, heat, sunlight, sweating, exercise, water, skin pressure, vibration, and scratching. This group is called chronic inducible urticaria because a specific physical condition brings on the welts.

When hives continue without a consistent trigger, the condition is called chronic spontaneous urticaria. Some cases involve an autoimmune process, meaning the immune system reacts against the body's own cells. This is not the same as having a weak immune system.

Stress does not usually explain hives by itself, but it can worsen itching or trigger flare-ups in some people. Alcohol, overheating, and anti-inflammatory pain medicines such as aspirin or ibuprofen may also aggravate existing hives in some people.

Hives are usually diagnosed from the appearance and behaviour of the rash. A healthcare professional may ask how long each welt lasts, how often the rash appears, and whether it follows food, medicines, infections, exercise, temperature changes, or pressure.

Photographs can help if the rash disappears before your appointment. Try to record when it began, how long individual welts lasted, and any swelling or other symptoms.

Most short-lived episodes do not need tests. Allergy testing may be useful when there is a clear pattern, such as hives appearing repeatedly soon after one particular food or exposure. Broad allergy panels are usually not helpful for chronic spontaneous hives because they can produce unrelated positive results.

Blood tests may be considered when symptoms are long-lasting or when there are signs of another condition. Tests are chosen according to your symptoms rather than performed routinely.

If physical hives are suspected, a specialist may use a controlled trigger, such as cold or pressure, to reproduce the reaction safely. A small skin sample, called a biopsy, may be needed if lesions are painful, last longer than expected, or leave bruising.

Treatment aims to control itching and prevent new welts while the episode settles. If a reliable trigger is found, reducing exposure may help. Many people, especially those with chronic spontaneous hives, never find one specific trigger.

Non-drowsy second-generation antihistamines are the main medicine used. They block the effects of histamine and generally cause less sleepiness than older antihistamines like cetirizine or loratadine. A clinician or pharmacist can help you choose a suitable product, particularly if you are pregnant, breastfeeding, taking other medicines, or have another health condition.

Do not increase the amount of an antihistamine or combine products unless a qualified healthcare professional has advised you to do so. Some antihistamines can affect alertness, driving, or alcohol tolerance.

Simple comfort measures may include cool compresses, loose clothing, fragrance-free skin products, and avoiding overheating. Scratching can intensify swelling, so keeping fingernails short may reduce skin damage.

For chronic hives that remain uncontrolled, a specialist may recommend additional treatment. Options include omalizumab, an injected medicine that reduces part of the allergic immune response. Other immune-modifying medicines are sometimes considered for difficult cases and require monitoring.

A short course of an oral corticosteroid may occasionally be used for a severe flare, but these medicines are not generally suitable for ongoing control because repeated or long-term use can cause significant side effects.

Adrenaline is used for anaphylaxis, not for routine hives. If you have been prescribed an adrenaline auto-injector because of a known severe allergy, follow your emergency plan and seek emergency care after using it.

Most hives settle without damaging the skin or internal organs. Individual welts generally disappear without scars, although scratching may cause broken skin or temporary colour changes.

Persistent itching can disturb sleep, concentration, work, school, and exercise. The unpredictable appearance of chronic hives may also affect mood or confidence.

Angioedema can be uncomfortable and may last longer than surface welts. Swelling limited to the face, hands, or feet is not always dangerous, but it should be assessed promptly if it is new, severe, or worsening.

Hives can occur during anaphylaxis, a severe allergic reaction involving breathing, circulation, or more than one body system. Hives by themselves are usually not anaphylaxis. Breathing difficulty, throat or tongue swelling, faintness, or sudden widespread symptoms after a likely allergen require emergency treatment.

Hives cannot always be prevented. This is especially true for chronic spontaneous hives, where no avoidable outside cause may exist.

If you have a confirmed trigger, reducing exposure can lower the chance of another episode. This might involve avoiding a particular medicine, using protection from cold, or changing how pressure is placed on the skin.

Do not stop a prescribed medicine without medical advice, even if you suspect it caused the rash. A clinician can assess the timing and decide whether an alternative is needed.

Restrictive diets are not routinely helpful when food is not a clear trigger. Removing many foods without guidance may cause poor nutrition and make it harder to identify what is actually happening.

Keeping a short symptom diary may reveal a repeatable pattern. Record the timing of welts, medicines, meals, infections, exercise, temperature exposure, and pressure on the skin. Avoid assuming that every event before a flare was its cause.

Acute hives often improve over hours or days, although some episodes continue for several weeks. New welts may appear while older ones fade. This does not necessarily mean that the condition is becoming more severe.

Chronic hives can come and go for months or years. Flare-ups may be frequent at first and later become less intense or less common. It is not possible to predict an exact timeline for one person.

Chronic spontaneous hives are usually not caused by something you are eating or touching. Repeatedly searching for hidden allergies can lead to unnecessary testing and restrictions. Regular follow-up is more useful when symptoms are continuing, changing, or not controlled by the current treatment plan.

Taking medicines as agreed, recording unusual triggers, and discussing side effects can help make treatment more manageable. If a first-line antihistamine is not controlling symptoms, routine follow-up allows the treatment approach to be reviewed.

Hives are not contagious. You cannot pass them to another person through touch, shared objects, coughing, or close contact.

Call emergency services if hives occur with:

• Trouble breathing, wheezing, or a tight throat
• Swelling of the tongue or inside the mouth
• Difficulty swallowing or speaking
• Fainting, severe dizziness, confusion, or collapse
• Sudden symptoms affecting several body systems after a likely allergen

Use a prescribed adrenaline auto-injector immediately if your personal emergency plan tells you to. Do not wait to see whether symptoms improve.

Seek prompt medical advice for rapidly worsening facial swelling, severe widespread hives, or symptoms that began after starting a new medicine. Swelling without hives can have other causes and may need separate assessment.

Arrange routine medical follow-up if hives last for six weeks, keep returning, disturb sleep or daily activities, or are not controlled by usual treatment. You should also arrange an assessment if individual marks remain longer than 24 hours, are painful, leave bruises, or occur with fever, joint pain, or feeling unwell.

Are hives contagious?

No. Hives are caused by chemical release within your own skin. They cannot spread to another person, although an infection that triggered them may sometimes be contagious.

Are hives always caused by an allergy?

No. Allergies can cause acute hives, but infections, medicines, physical triggers, and immune system activity can also cause them. Chronic spontaneous hives often have no specific allergic trigger.

How long do hives last?

Each welt usually fades within 24 hours. An episode may last from hours to several weeks because new welts can keep appearing. Hives occurring on most days beyond six weeks are considered chronic.

Can stress cause hives?

Stress may worsen a flare or make itching more noticeable. It is not always the underlying cause, and ongoing symptoms should not automatically be attributed to stress.

Do hives leave scars?

Typical hives do not leave scars. Scratching may damage the skin, and temporary darker or lighter marks can follow inflammation. Fixed, painful, or bruising spots need assessment because they are not typical.

Should I avoid certain foods?

Avoid a food when there is a confirmed allergy or a clear, repeatable connection with symptoms. Broad food avoidance is unlikely to help chronic spontaneous hives and may lead to nutritional problems.