What causes hives and how to identify it?

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Causes

Hives can develop as a reaction to:

• an allergen
• another physical trigger, such as extreme temperatures
• an underlying health condition

Sometimes there is no clear reason why they occur. In the case of chronic hives, some experts believe that it may result from an autoimmune reaction, but they are still unsure.

Allergens

Hives can develop when the body reacts to an allergen. When an allergic reaction occurs, the body releases a protein called histamine. Next, tiny blood vessels called capillaries leak fluid. This fluid accumulates in the skin and causes inflammation and a rash. As fluid accumulates under the skin, small bumps form.

The reaction can occur if a person consumes something or touches something that they are allergic to. This is known as “contact urticaria.”

If acute hives results from an allergic reaction, the cause may be:

• a medication, such as:
  • some antibiotics
  • some nonsteroidal anti-inflammatory drugs, or NSAIDs, such as aspirin
  • angiotensin converting enzyme inhibitors, which are drugs for high blood pressure
• nuts, eggs, seafood, or another food allergen
• latex
• kiwi, banana, chestnuts, or mango, in people with a latex allergy
• some plants, including nettles, poison ivy, and poison oak
• additives in some foods, cosmetics, and other products

What are the effects of a latex allergy?

Physical triggers

A physical factor other than an allergen can cause hives.

Here are some possible triggers:

• sunlight exposure
• scratching or rubbing the skin
• pressure, from a tight belt, for example
• extreme temperatures or changes in temperature
• a high body temperature, due to sweating, exercise, anxiety, or a hot shower
• adrenalin, which the body releases during exercise and exposure to heat or stress
• UV light from a tanning bed
• water on the skin, in rare cases
• vibration, in rare cases

Underlying health conditions

Some examples of health conditions that can cause hives include:

• viral infections, such as the flu, the common cold, glandular fever, or hepatitis B
• bacterial infections, such as some urinary tract infections and strep throat
• intestinal parasites, such as Giardia lamblia
• autoimmune hypothyroidism
• autoimmune conditions, such as rheumatoid arthritis, systemic lupus erythematosus, Sjögren’s disease, celiac disease, and type 1 diabetes
• any other condition that causes inflammation of blood vessels

Chronic hives may start as an autoimmune response, but the exact cause is unclear.

Symptoms

Hives often has these features:

• The characteristic raised skin lesions can appear in any area of the body.
• The lesions often appear in batches.
• They tend to be itchy.
• They may be pink, red, or skin-colored.
• If a person presses in the middle, the coloring may fade.
• The bumps usually last no longer than 24 hours, but new ones may form.
• Their size can range from that of a pinprick to several inches across.

Hives does not always appear as bumps. The lesions may also be:

• tiny spots
• blotches
• thin, raised lines

The time it takes for the lesions to appear depends on the cause.

In someone with contact urticaria, the skin reacts to an allergen, such as latex or an irritant. The reaction occurs 10–60 minutes after exposure to the allergen and lasts up to 24 hours.

In a person with a food allergy, hives usually appear within 1 hour. Reactions to food colorings and other additives can appear after 12–24 hours. A reaction to a drug can appear at once or much later, even years after starting to use the medication.

In some cases, hives persists for several days. People with chronic hives can have the symptoms for months or years.

Hives on different parts of the body

Hives can appear anywhere on the body, such as the:

• legs
• arms
• trunk
• face

Hives on the legs

Some people have “papular urticaria” in reaction to insect or spider bites. It usually affects children who have not yet developed immunity to these bites. The lesions can develop anywhere, but commonly occur on the legs.

Below are some typical features:

• The characteristic itchy red bumps, known as papules, form in clusters.
• Each papule measures 0.2 to 2.0 centimeters across and has a central point.
• They may be fluid-filled.
• New papules may appear as old ones disappear.
• A new insect bite may cause papules to reappear.

Hives on the face

When hives results from an allergy or sensitivity reaction, it can significantly affect the face, for example, by causing swelling in the lips.

The swelling can become more widespread and affect the mouth, throat, and airways. In this case, the person may find it hard to breathe. This is an emergency, and the person needs urgent medical care. They are at risk of developing a life threatening condition called anaphylaxis.

If the person has an autoinjector, start by helping them use it. Then, call 911, or the local emergency number, and stay with the person until help comes. If a specific object appears to have triggered the reaction, it may be helpful to take a sample to the hospital.

Anaphylaxis

Anaphylaxis is a severe allergic reaction that can affect the whole body.

It can lead to serious breathing difficulties and a loss of consciousness. It is a medical emergency and can be fatal if treatment is delayed.

If a person develops hives, they need to be aware of any further symptoms that could indicate an anaphylactic reaction.

Immediate medical attention is necessary if the person experiences:

• nausea and vomiting
• swelling of the lining of the mouth, tongue, lips, and throat, causing difficulty breathing
• cold, clammy skin
• a rapid heartbeat
• faintness or lightheadedness
• an unexpectedly abrupt feeling of intense anxiety

Hives vs. other rashes

Hives are a kind of rash. If someone has hives, the rash typically has these features:

• It is raised and itchy.
• There may be swelling under the affected skin.
• There may be papules or plaques.
• The affected areas of skin can expand and join together.
• The rash may be pink, red, or skin-colored.
• The center turns pale in the middle if someone presses on it.
• Each bump may last less than 24 hours, but other bumps may replace it.
• The bumps can seem to appear and disappear and change shape or location suddenly.

Is it contagious?

Hives is not contagious. However, if it stems from an underlying infection, that infection could be contagious. Examples of these infections include the flu, the common cold, glandular fever, also known as mono, and hepatitis B.

Also, if hives result from pests, such as dust mites, other people nearby might have the same reaction.

Treatment

The best approach to treatment depends on the cause and whether the issue is acute or chronic.

Acute urticaria

If symptoms are mild and occur after exposure to an allergen or irritant, home remedies can usually soothe the itchiness until the rash disappears.

Options that a doctor may recommend include:

• non-sedating antihistamines, such as cetirizine (Zyrtec) or fexofenadine (Allegra)
• short-term use of topical steroids
• antiseptic creams to prevent a secondary infection
• soothing creams to reduce itchiness

If there are signs of allergy, and the person has swelling in their lips, face, or tongue, the doctor may prescribe an epinephrine auto-injector to carry for use in emergencies.

Chronic urticaria

A person with chronic urticaria may need to take antihistamines regularly until their symptoms resolve.

Omalizumab (Xolair) is an injectable drug that blocks immunoglobulin E, a substance that plays a role in allergic responses. It can reduce symptoms of chronic spontaneous urticaria, a type of hives with an unknown origin.

Meanwhile, a 2016 review concluded that acupuncture might help relieve chronic urticaria, though there is not enough evidence to confirm that this is a safe, effective treatment.

Chronic hives can lead to severe discomfort, distress, and possibly depression. Stress, too, can aggravate hives. And having hives can worsen stress. Anyone who feels that hives is affecting their quality of life or mental well-being should speak with a doctor.

If tests reveal an underlying disease, such as lupus, the doctor will recommend treatment for this.

Learn more about hives treatments.

Home remedies

Tips for reducing hives symptoms include:

• using a soothing lotion or cool compresses to ease the itchiness
• wearing loose, light, cotton clothing
• avoiding scratching
• choosing soaps, moisturizers, and other cosmetics for sensitive skin
• avoiding overheating by taking cold showers and using a fan
• avoiding sun exposure
• avoiding exposure to known triggers

There is some evidence that supplements, such as vitamin D3, can help treat chronic hives. However, there is currently not enough evidence to confirm that they work.

It is important to speak with a healthcare professional before using supplements, as these can trigger adverse reactions. Some supplements and vitamins contain substances that can trigger hives.

Preventing hives

Tips for preventing hives may include:

• choosing mild or fragrance-free soaps, skin creams, and detergents
• taking over-the-counter antihistamines when the pollen count is high, if pollen may be a trigger
• keeping a record of any possible triggers, such as a food diary
• talking to a doctor about whether medications may be responsible
• using meditation and other relaxation techniques to manage stress

Almost any food can cause an allergic reaction. Some common triggers include:

• milk
• eggs
• nuts
• soy
• wheat
• seafood
• sesame

Keeping a record of meals and symptoms can help identify which foods are triggering the reaction.

Learn more about foods that commonly cause allergies.

Hives and stress

One trigger for acute hives may be adrenalin, the American Academy of Dermatology explains.

Research has linked persistent stress with a mild underlying infection in people with chronic urticaria, and experts are interested in finding out whether these issues have a shared underlying mechanism.

Managing stress through meditation, exercise, or counseling may help some people with chronic hives manage their symptoms.

Diagnosis

To diagnose hives and make a treatment plan, a doctor first needs to determine whether the issue is acute or chronic.

Acute urticaria

First, the doctor, who may be a dermatologist, examines the affected areas. Next, they try to identify the trigger.

They often ask:

• when and where the rash began
• about exposure to likely triggers, such as latex gloves, chemicals, or an insect bite
• about any current medications, including herbal supplements
• about the person’s medical history
• whether there is any family history of hives

Often, the trigger is unclear. If there is a likely trigger, the doctor might refer the person to an allergy clinic. If they suspect a food allergy, they may suggest keeping a food diary.

At an allergy clinic, a specialist may do a skin prick test to find out whether there is an allergy to specific substances, such as chemicals, dust mites, or specific foods.

However, a doctor does not usually recommend extensive allergy testing for a single episode of hives.

Chronic urticaria

Most cases of hives resolve after 6 weeks, but around 8% persist for longer. This is chronic urticaria. A doctor may recommend blood tests and other tests to identify the underlying cause, though pinpointing the cause is not always possible.

Chronic urticaria is unlikely to result from an allergy or contact with an irritant, so doctor will probably not recommend a skin prick test.

Takeaway

Hives, or urticaria, is a kind of rash. It may result from an allergy, another trigger such as adrenalin, an underlying health condition, or other factors. Acute hives starts suddenly and resolves within 6 weeks, while chronic hives can last for months or years.

If a person knows that something specific, such as seafood, triggers hives, they may be able to avoid it. However, the cause of hives is not always clear, so prevention is not always possible.

If hives is affecting the quality of life, speak with a doctor. They can recommend treatment and check whether an underlying health issue is the cause.

If hives occurs with swelling in the mouth or throat, nausea, faintness, a rapid heartbeat, or cold, clammy skin, the person may have a life threatening condition called anaphylaxis, and they require immediate medical care.