Urticaria (Hives or Angioedema) info

Urticaria (more commonly known as "hives" in laypeople's terms") is a medical condition characterized by raised, red, and usually very itchy circles of various size that appear and disappear on the skin. Although they only affect the skin, hives can cover large areas of the body in some cases. Urticaria is also known as nettle rash or uredo.

These red skin patches can range in diameter, they often have a pale border and cause a severe and relentless itchy sensation. They usually appear as a result of an adverse reaction to certain allergens or for unknown reasons.

Angioedema is a tissue swelling similar to urticaria, but the swelling occurs beneath the skin instead of on the surface. Angioedema is a much more serious condition. Angioedema is characterized by deep swelling around the eyes and lips and sometimes swelling of the genitals, hands, and feet.

Angioedema generally lasts longer than urticaria, but the swelling usually goes away in less than 24 hours. This can be a very dangerous condition because, angioedema of the throat, tongue or the lungs can block the airways, causing difficulty breathing and thus even potentially becoming life-threatening, even though this happens really rarely.

How common are urticaria and angioedema?

Urticaria affects 15 to 20% of the general population in the US and around the world. One in five people will experience acute hives or angioedema at some time of their life. Hereditary angioedema affects only about 6,000 people in the United States. Incidence rates for acute urticaria are similar for men and women, although chronic urticaria occurs more frequently in women.

Types of urticaria and angioedema

Acute Urticaria

The acute type of hives lasts less than six weeks, and often only a few days to a week. The most common causes of acute urticaria are:  

• food
• medications
• latex
• infections
• environmental factors (pollen, chemicals, plants, dander, dust, mold)
• emotional stress
• insect bites
• internal diseases

The most common foods that can cause hives includes nuts, chocolate, fish, tomatoes, eggs, fresh berries and milk. This kind of hives will affect some people with allergies to these foods.

Among the most common medications that can cause hives and angioedema are:

• Aspirin
• Nonsteroidal anti-inflammatory medications
• Ibuprofen, high blood pressure medications (ACE inhibitors) or
• Pain-killers such as codeine

Chronic Urticaria and Angioedema

Hives that last more than six weeks are called chronic urticaria. The cause of this type of hives is usually more difficult to identify than that of the acute urticaria, and the fact is that the cause remains unknown in more than 80 percent of patients. Chronic urticaria and angioedema can affect internal organs and can cause symptoms such as shortness of breath, vomiting, and diarrhea.

Chronic urticaria and angioedema can also be caused by several other conditions such as:

• emotional stress
• heat
• exercise
• chronic medical illness, such as hyperthyroidism, SLE, rheumatoid arthritis
• pregnancy

Physical Urticaria

This is the type of hives caused by the direct physical stimulation of the skin such as cold, heat, sun exposure, vibration, pressure, sweating, exercise and others. Most experts believe that there is a completely different mechanism behind this type of urticaria. The hives usually occur at the site of direct stimulation and rarely appear on other areas of the skin. Most of the hives appear within one hour after the exposure.

There are several sub-types of physical urticaria and the most common ones are:

• Aquagenic: Reaction to water
• Cholinergic: Reaction to body heat
• Cold: Reaction to cold, such as ice, cold air or water
• Delayed Pressure: Reaction to standing for long periods, bra-straps, belts
• Heat: Reaction to hot food or objects
• Solar: Reaction to direct sunlight
• Vibration: Reaction to vibration
• Adrenergic: Reaction to adrenaline 

Dermatographism

Dermatographism is a very common type of urticaria and most experts will consider it to be part of the physical urticaria group. Anyone can experience this kind of hives at some point in life because this type of hives is considered a normal variant of the skin. This type of hives forms after firmly stroking or scratching the skin.  

Symptoms and signs

Hives

Acute hives can be present on your skin for up to six weeks, while chronic hives last even longer. Hives are raised, red bumps of various sizes that appear on your skin and usually subside on their own. They're often itchy and may look similar to (very inflated) mosquito bites. Hives could be localized all over the body, depending on the place where the allergen came into contact with the body, and depending on the cause.

Angioedema

Angioedema is a condition that can look similar to hives, but occurs deeper in the skin. Signs and symptoms of angioedema include large welts or swelling of the skin that may occur in the following locations:

• Near your eyes and lips
• On your hands
• On your feet
• On your genitalia
• Inside of your throat

When angioedema affects the throat, hindering your ability to breathe, it is a serious medical emergency.

Hereditary angioedema

Hereditary angioedema occurs in about 1 in 100,000 people. These patients lack an effective enzyme, which is associated with swellings of the face, throat or limbs. This type of angioedema is accompanied with several symptoms and the most common are:

    * Sudden and severe swelling of your face, arms, legs, hands, feet, genitalia, digestive tract and airway
    * Abdominal cramping as a result of digestive tract swelling
    * Difficult or obstructed breathing due to swelling of your airway

Pathophysiology of the condition

Experts have proven that urticaria is caused by the release of several mediators such as histamine, bradykinins, kallikrein, or acetylcholine, resulting in intradermal edema from capillary and venous vasodilatation and occasional leukocyte infiltration.
There are two possible mechanisms that could be responsible for the urticaria and we will look at them now.

Immunologic mechanism

This mechanism is explained by the theory that all the manifestations of acute urticaria are caused by immunoglobulin E mediated hypersensitivity with histamine released from mast calls as its primary mediator. It also may be the result of the complement-mediated reactions or specific drug reactions.

Non-immunologic mechanism

There are several theories that tried to explain this type of urticaria. According to some experts, mediators can be released from mast cells without IgE and immunologic reaction. Some people have inherited weakness of the mast cells walls. Physical urticaria can be caused by the direct physical contact and without any immunologic reaction.
 

Risk factors

A person may be at greater risk of developing both hives and angioedema if he or she has or had:

• hives or angioedema before
• other allergic reactions             
• a family history of hives or angioedema
• a family history of hereditary angioedema

Diagnosis of urticaria

A doctor should ask many questions in an attempt to find the possible cause because, in most cases, this can be very difficult. Since there are no specific tests for hives or the associated swelling of angioedema, testing will depend on your medical history and a thorough examination by your dermatologist. Skin tests may be performed to determine the substance that you are allergic to.  
There are several lab studies that could confirm the diagnosis and the most common are:

• Stool examination for fecal ova, and parasites
• Antinuclear antibody titer
• Hepatitis B and C screen
• Thyroid function tests
• Tests for CBC (complete blood count), prostate-specific antigens, and serum calcium

Treatment of urticaria and angioedema

The standard treatment for hives and angioedema is antihistamines, which block the symptom-producing release of histamine, the chemical that leads to a swollen skin rash.

Antihistamines

Oral antihistamines control itching for the majority of patients with urticaria, but the problem is that they do not affect the underlying cause of the rash. Antihistamines may need to be taken intermittently or continuously until the underlying tendency toward urticaria disappears. Some of the most commonly used non-sedating antihistamines are:

• loratidine
• fexofenadine
• terfenadine
• cetirazine, and
• astemizole

Patients should also keep in mind that these antihistamines may be unsuitable during pregnancy. Terfenadine and astemizole may increase the risk of abnormal heart rhythms. 

Corticosteroids

For severe hives or serious types of angioedema, doctors may prescribe an oral corticosteroid drug, most commonly prednisone, which can help reduce swelling, redness and itching. These steroid medications stabilize mast cell membranes and inhibit further histamine release. They also reduce the inflammatory effect of histamine and other mediators, and can provide symptom relief quickly.

Other medications

It is very important to remember that these medications are often ineffective in treating hereditary angioedema. Medications used specifically to treat the hereditary form of this condition on a long-term basis include certain androgens, such as danazol (Danocrine®), that help regulate levels of blood proteins. Sometimes, only an urgent medical intervention can save the life of the patient because, in cases of a severe and serious attack of hives or angioedema, a patient may need an emergency injection of adrenaline and a trip to the emergency room to allow them to clear their airways.

Other medications include:

• Ultraviolet radiation treatment
• Antibiotics and antifungal agents, used to clear an assumed underlying infection or for non-specific anti-inflammatory action.
• Immunosuppressive medications
• Antifibrinolytic agents
• Tricyclic medications such as amitriptyline, nortriptyline and doxepin

Self care for hives and angioedema

Here are some of the most useful tips for the future self care, should you ever find yourself suffering from an episode of hives:

• Avoid irritating affected areas.
• Take cool showers.
• Reduce your intake of acidic fruits.
• Apply cool compresses.
• Wear loose, light clothing.
• Avoid alcohol (it causes the surface blood vessels to dilate).
• Minimize vigorous activity, which can release more irritants into the skin.
• Use over-the-counter antihistamines to help relieve the itching
• Cool the affected area with a fan, cold flannel, ice pack or soothing lotion.