Urticaria is a type of hive or raised red bumps on the skin. The bumps are usually itchy and linked to swelling. Between 15 and 20 percent of people get hives at some point during their life.1
Different types of hives are defined using several factors:1,2
- Length of episodes – Acute (less than 6 weeks) or chronic (longer than 6 weeks)
- Cause of hives – Idiopathic (no known cause) or physical (environmental triggers)
About 30 percent of urticaria cases are chronic. And more than 80 percent of people with chronic hives have no known cause. This type of hives is called chronic idiopathic urticaria (CIU).1,2
Treatment for any type of chronic hives is similar. But it may be helpful to know whether you have physical triggers. This can help you avoid exposures that worsen your symptoms.
Acute versus chronic hives
Hives that last for less than 6 weeks are considered acute. This means they quickly come and go away on their own. Allergic reactions to foods and medicines often cause acute hives.2,3
When hives last for more than 6 weeks, the condition is considered chronic. Usually, individual hives will only last 24 hours. But symptoms happen most days of the week for at least 6 weeks. The cause of chronic hives is usually not known.2,3
The symptoms of acute and chronic hives look the same. This makes it hard to distinguish between them when hives first appear. However, 2 out of every 3 cases of hives end up being acute.2,3
Idiopathic or spontaneous hives
More than 80 percent of chronic hives cases are considered idiopathic. This means that the cause cannot be identified. Doctors must rule out potential causes of hives, such as allergies or physical exposures. Another term to describe this type of hives is spontaneous.2
Even though there is no known cause, physical exposures may worsen symptoms. However, in idiopathic hives, these are not the main or only causes.2
Physical or inducible hives
In physical hives, 1 or more physical triggers cause hives. About 15 percent of cases of chronic hives are physical. This type of hive is also called inducible because a certain physical trigger induces hives. Some common types of physical urticaria are triggered by things like:1
- Cold
- Stroking or scratching
- Pressure
- Water exposure
- Heat, exercise, or stress
- Sun exposure
- Vibration
Most people with physical hives have only 1 physical trigger. Some people have hives triggered by multiple things. Doctors diagnose physical urticaria based on health history and certain challenge tests.4
Other types of hives
Autoimmune urticaria
About half of cases of idiopathic hives seem to involve an autoimmune reaction. This means that your immune system mistakenly attacks healthy cells. This could cause your cells to release histamine, leading to hives. Histamine is a chemical that causes many of the symptoms of allergies.1
Hives are also linked to a number of autoimmune conditions. This includes lupus, rheumatoid arthritis, and thyroid disease. We do not know if autoimmune urticaria is a separate type of hives or a feature of many types.1
Urticarial vasculitis
Vasculitis is inflammation of the blood vessels. This can cause hives that are more painful than itchy. Hives that last for more than 24 hours in 1 location are often a sign of vasculitis.1,5
Doctors can diagnose vasculitis using a health history, physical exams, lab work, and a skin biopsy. Treatments are similar to other types of hives but may use steroids more often.5
Pseudoallergic urticaria
A pseudoallergy looks like an allergic reaction but does not show any signs of an immune reaction. For example, food intolerances are a type of pseudoallergy. Some cases of idiopathic hives seem to involve a pseudoallergy to food ingredients.1
Some food ingredients linked to a pseudoallergy response include:1
- Preservatives
- Sweeteners
- Artificial food dyes
- Wine
- Salicylic acid
- Alcohol
- Dietary fats
People with chronic hives often say that certain foods worsen symptoms. These foods are different for everyone but can include shellfish, eggs, nuts, and strawberries.1
Infections
Some research has linked chronic hives to different infections. However, there is not strong evidence of these links. Some infections reported to cause hives include:1
- Hepatitis B virus
- Streptococcus and mycoplasma species
- Mycobacterium tuberculosis
- Herpes simplex virus
