Pictures to Help With Identifying Hives vs. Other Skin Rashes

Hives, also known as urticaria, are a type of skin rash with raised, red, itchy bumps or welts. Hives are a common condition that affects up to 20% of the population at one time or another.

Hives can affect any person at any age on any part of the body in any season of the year. They can be as size as the tip of a pen or as large as a dinner plate. Hives can also cause stinging or burning sensations. The itching is typically worse at night and can interfere with sleep.

In this gallery of images, you will view several types of hives and the important characteristics of each. The article will also explain why different hives develop and what can be done to treat them.

Hives Caused by Infection

Hives are often idiopathic, meaning that they can develop spontaneously for no known reason.

If a cause can be found, it is most often the result of a reaction to one of the following:

• Allergic reactions to food, medications, or insect bites
• Bacterial or viral infections, including strep throat, colds, and mononucleosis
• Physical triggers like cold temperatures, pressure, scratching, or vibrations
• Sweating events like exercise or being in an overheated environment
• Psychological stress
• Sun exposure (uncommon)
• Water exposure (uncommon)

This photo is an example of hives caused by a ​viral infection. Hives caused by an infection tend to be generalized (widespread) rather than localized (as can occur with things like a bug bite).

Chronic Hives

Hives can usually be diagnosed based on their appearance. The hives may be acute, meaning that they develop rapidly and tend to resolve quickly. They may also be chronic, meaning that they persist for more than six weeks and/or recur frequently over months or years.

Chronic hives are most often idiopathic and will develop spontaneously for no apparent reason. It is thought that some sort of autoimmune disorder may be involved.

Chronic hives may also be inducible, meaning that a known trigger causes them. One such example is hives that develop after wearing a tight belt or clothing, referred to as pressure-induced urticaria.

People with chronic hives tend to have co-occurring atopic (allergy-related) conditions like asthma, atopic dermatitis (eczema), and allergic rhinitis (hay fever).

Chronic hives tend to cause splotchy welts, as in this picture, with raised edges and defined borders.

Acute Hives

Acute hives are common and tend to be harmless, Most clear up within a day and don't leave any lasting marks. This is a picture of acute hives.

A doctor may prescribe an oral antihistamine to help relieve the itching or recommend simple home remedies to help relieve the discomfort. Fortunately, most cases resolve on their own.

This doesn't mean that all cases of acute hives are harmless. If hives develop suddenly and are accompanied by shortness of breath, wheezing, and the swelling of the face or tongue, it could be a sign of a potentially life-threatening, whole-body allergy known as anaphylaxis.

Other signs of anaphylaxis include dizziness, irregular heartbeats, and a feeling of impending doom. 911 emergency assistance is needed.

Spongy Hives

Hives are caused when the immune system responds abnormally to certain physical, environmental, and even psychological triggers.

When this happens, the immune system will instruct immune cells in the skin (called mast cells) and immune cells in the blood (called basophils) to break open and release inflammatory chemicals, including histamine, into the body.

Histamine causes tiny blood vessels in the skin to widen in order for larger immune cells to access the site of the supposed injury. The widening causes fluids to leak into surrounding tissues, causing the raised, red welts we recognize as hives.

Depending on the amount of fluid that gets released, hives can look very "spongy" like this. Or, they can appear flat with well-defined, raised borders.

Dermatographism

When people refer to hives, they often think of an allergic response to food or medications. But, hives can also be caused by physical stimuli that cause the skin to form raised, red welts.

One example is dermatographism. Dermatographism is a form of chronic urticaria caused by stroking the skin with pressure. The term "dermatographism" literally means the ability to write on the skin.

Dermatographism is among the most common forms of hives, affecting anywhere from 2% to 5% of the world's population. Even so, the exact cause of this condition is largely unknown.

Similar conditions include cold-induced urticaria, pressure-induced urticaria, exercise-induced urticaria, and stress-induced urticaria.

Summary

Hives (urticaria) are a type of rash that causes raised, red, itchy bumps or welts. Hives may be acute, appearing quickly and usually resolving quickly on their own. Or, they may be chronic, lasting for more than six months and/or recurring frequently over months or years.

There are many possible causes of hives, including allergies, infections, stress, cold, vibration, exercise, and even scratching. Chronic hives are often idiopathic, meaning of unknown origin, and may develop spontaneously for no apparent reason.

Hives are ultimately caused by an abnormal immune response in which inflammatory chemicals, including histamine, are released into the bloodstream and tissues. Antihistamines may be used to relieve the swelling, redness, or itchiness of hives. Many cases clear up on their own without treatment.