Types and Classification
Urticaria is a common skin disease, afflicting approximately one in five individuals at some point during their life. It manifests as sudden wheals on the skin, often accompanied by deep swelling known as angioedema. Some patients experience angioedema without wheals. These urticaria-typical skin changes can be either localized (wheals, angioedema) or affect the entire body (wheals). Urticaria is classified as acute or chronic according to its duration and as inducible or spontaneous according to the role of certain triggers.
CAUSES
Urticaria develops when specific immune cells in the body, called mast cells, become activated via their surface receptor FcεR1 by the acton of autoallergens or autoantibodies. This causes vessels to dilate, and become leaky and mediates activation of sensory nerves. As a result, fluid, immune cells and their messenger substances such as histamine accumulate in the skin and cause redness, swelling and itching. Urticaria can arise from various factors including acute infections, drug or insect bite reactions, and in very rare cases, food allergy. However, in the vast majority of cases the cause is not clearly identifiable.
Acute Urticaria
Acute urticaria is characterized by the occurrence of wheals and/or angioedema lasting 6 weeks or less. Most cases of acute urticaria resolve within 1 week.
Learn about acute urticaria by watching the UCARE 4U video about this topic.
Triggers
In acute urtiaria symptoms are either elicited by specific triggers (inducible urticaria), or appear spontaneously. Symptoms may exacerbate by unspecific triggers that increase disease activity such as drugs (e.g. NSAID family drugs as diclofenac, asprin, ibuprofen), infections, stress, or food.
Testing
Apart from anamnesis for possible trigger factors, and unless strongly suggested by patient history (e.g. presence of allergy) acute urticaria, because it is self-limiting, usually does not require a diagnostic workup (1).
Most cases of acute urticaria are non-allergic and, although bothersome, are not dangerous. The exception is a rare and severe allergic condition, so called anaphylaxis, that may appear with cutaneous symptoms of acute urticaria and may be life-threatening if left untreated. Therefore, in acute urticaria, it is crucial first to identify possible allergic triggers such as food or drugs to exclude your acute urtiaria being a cutaneous symptom of anaphylaxis. If your acute urticaria is suspected to be due to a type I food allergy or drug hypersensitivity (especially for non-steroidal anti-inflammatory drugs/NSAIDs such as diclofenac, ibuprofen and aspirin) allergy testing is recommended. Avoidance of any known trigger of your urticaria is the most crucial step to avoid recurrence in the future.
Treatment
Pharmacological treatment (see treatment section) may be necessary to control symptoms (1). Your doctor is the primary contact person to give you more information on the available options.
Chronic Urticaria
Chronic urticaria is defined as the occurrence of wheals and/or angioedema for more than 6 weeks. In the course of chronic urticaria, daily or almost daily symptoms or frequent symptom-free periods, that may even last for weeks or years, can occur. Less than 40% of acute urticaria cases become chronic. As a frequent clinically significant variant, chronic urticaria is subdivided into spontaneous (chronic spontaneous urticaria/CSU) and inducible (chronic inducible urticaria/CIndU) subtypes. While chronic spontaneous urticaria constitutes the bulk of patients with chronic urticaria, chronic inducible urticaria is less frequent. In a minor proportion of patients with chronic urticaria, both form, CSU and CIndU, may be present.
Learn about chronic urticaria by watching the UCARE 4U video about this topic.
Chronic Spontaneous Urticaria (CSU)
The spontaneous form of chronic urticaria, also known as chronic spontaneous urticaria (CSU) is characterized by the sudden (out of the blue) appearance of itchy wheals, angioedema, or both in the absence of a definite trigger. Yet, various unspecific triggers have the potential to cause flare-ups or to worsen CSU.
The UCARE experts from Global Allergy and Asthma Excellence Network explain more about CSU in the UCARE 4U video about chronic urticaria.
Triggers
Symptoms may exacerbate by unspecific triggers that increase disease activity such as drugs (e.g. NSAID family drugs as diclofenac, asprin, ibuprofen), infections, stress, or food.
Testing
To confirm diagnosis and exclude differential diagnoses, in CSU, the diagnostic workup includes a thorough history, physical examination (including review of pictures of wheals and/or angioedema), basic tests, and the assessment of disease activity, impact, and control. The basic tests include a differential blood count and CRP and/or erythrocyte sedimentation rate, in all patients, and total IgE and IG-anti-TPO in patients in specialist care and more biomarkers as appropriate. Based on the results obtained by these measures, further diagnostic measures based on the patient history and examination, especially in patients with long-standing and/or uncontrolled disease is recommended.
Treatment
In addition to minimizing exposure to (drugs, stress, food) or eradication of (infections) unspecific exacerbating triggers as far as possible, pharmacological treatment (see treatment section) is a major component of CSU management to control symptoms (1).
Your doctor is the primary contact person to give you more information on the available options.
Chronic Inducible Urticaria (CIndU)
The inducible form of chronic urticaria, also known as Chronic Inducible Urticaria (CIndU), is characterized by the appearance of itchy wheals, angioedema, or both in the presence of a definite subtype-specific trigger. Wheals and/or angioedema always occur when the trigger is present and never when it is absent.
Triggers
Each sub-form of inducible urticaria has its own trigger. Depending on the nature of their triggering factors, the individual medical conditions are divided into symptomatic dermographism (friction), cold urticaria (cold), delayed pressure urticaria (pressure), solar urticaria (light), heat urticaria (heat), vibratory angioedema (vibrations), cholinergic urticaria (increase in body core temperature), contact urticaria (skin contact with triggering agents) and aquagenic urticaria (water).
Testing
In patients with CIndU, the routine diagnostic workup aims to exclude differential diagnoses, to identify the subtype of CIndU, and to determine trigger thresholds. The last of these is important as it allows for assessing disease activity and response to treatment. For most CIndU subtypes, validated tools for provocation testing are available.
Treatment
In addition to avoiding the eliciting triggers as far as possible, pharmacological treatment (see treatment section) may be necessary to control symptoms (1).
Your doctor is the primary contact person to give you more information on the available options.
Types of Inducible Urticaria
Symptomatic Dermographism (Dermographic urticaria or urticaria factitia)
Symptomatic dermographism is the most common subtype of CIndU characterized by the development of linear wheals in response to friction by stroking, scratching, scrubbing, or rubbing Symptoms appear to be as if someone has been writing on the skin within 1-10 minutes following friction It is important to note that the skin manifestations never occur spontaneously, but exclusively appear only in response to the trigger. Symptomatic dermographism should be differentiated from red dermographism, that causes redness of the skin, that is not raised and does not itch. This reddening of the skin is normal and not pathological.
Triggers
Symptoms of symptomatic dermographism appear in response to friction by e.g. stroking, scratching, scrubbing or rubbing.
Testing
Symptomatic dermographism can be identified through a detailed medical history. The diagnosis can be confirmed by provocation testing using a wooden spatula or specialized instruments like dermographometers such as Dermographic Tester or FricTest®. Firm pressure is applied to the skin in a stroking motion.
Treatment
The management of symptomatic dermographism involves the avoidance of eliciting stimuli as far as possible, including the avoidance of tight clothing and removal of tags etc. In addition to avoiding the eliciting triggers as far as possible, pharmacological treatment (see treatment section) may be necessary to control symptoms (1).
Your doctor is the primary contact person to give you more information on the available options.
Cold Urticaria or Cold Contact Urticaria
Cold urticaria is characterized by the rapid appearance of itchy wheals, angioedema or both on the skin in response to cooling. Cold urticaria is the second most common type of inducible urticaria. Wheals and angioedema occur within minutes of exposure and is limited to the exposed areas of the skin; however, prolonged, extensive cold exposure (e.g. swimming in cold water) can trigger severe systemic reactions/anaphylaxis (shortness of breath, drop in blood pressure, loss of consciousness, choking sensation etc.). Each patient has a temperature level (threshold) below which symptoms are triggered. Temperature above this level does not trigger the onset of wheals. The higher the temperature threshold, the more frequent is the occurrence of wheals on cold exposure.
Triggers
Symptoms of cold urticaria develop in response to cooling like contact with cold wind, air, water, food or objects.
Testing
The diagnosis of typical cold urticaria is suggested from the patient´s symptom history and confirmed by standard provocation testing. Types of standardized tests in clnical practise include the application of a cold object on the skin ( the ice cube test ) or use of electronic testing devices like the TempTest®, to identify the temperature level (threshold) at which the symptoms occur Unusal responses (delayed whealing) or the need for specific provocation methods (e.g. total body cooling) are associated with atypical forms. Clinical presentations may vary ranging from mild localized whealing to cold-induced anaphylaxis.
Treatment
Management of cold urticaria includes avoiding cold exposure, wearing warm clothing when appropriate. High-risk situations like exposure to cold baths, swimming, cold foods, beverages etc. should be avoided. Complete avoidance of cold exposure may be difficult. Emergency treatment should be available since cold urticaria bears a certain risk of systemic reactions.
In addition to avoiding the eliciting triggers as far as possible, pharmacological treatment (see treatment section) may be necessary to control symptoms (1).
Your doctor is the primary contact person to give you more information on the available options.
Solar Urticaria/Light Urticaria
Solar urticaria is a rare type of inducible urticaria. In solar urticaria, itchy wheals appear on the skin within minutes of exposure to light (i.e. visible sunlight, components of solar radiation, artificial light). Parts of the skin not exposed are usually unaffected.
Triggers
Symptoms of solar urticaria are triggered by direct exposure to visible sunlight, components of solar radiation, or even artificial light. Light exposure of skin areas through light clothing and glass can also result in formation of wheals as these do not completely block UV rays and visible light. The severity of symptoms may increase with the intensity of exposure.
Testing
Diagnosis of solar urticaria is made based on patient history, exclusion of differential diagnoses and provocation testing by phototesting, i.e. exposing different skin areas to different wavelengths of light (e.g. visible light, UV-A and UV-B). Sunscreens and photoactive medications should be avoided before photo testing. Novel diagnostic methods using a basophil activation test with irradiated patient’s serum to assess serum photoallergens might be helpful in cases where light provocation tests are negative. Importantly, accurate determination of the range of eliciting wavelengths may be important for the appropriate selection of sunscreens or for the selection of light bulbs with an UV-A filter.
Treatment
Patients with solar urticaria should avoid exposure to direct sunlight, wear protective clothing and use high protection sunscreens. Emergency treatment should be available since solar urticaria bears a certain risk of systemic reactions. In addition to avoiding or protection from eliciting triggers as far as possible, pharmacological treatment (see treatment section) may be necessary to control symptoms (1).
Your doctor is the primary contact person to give you more information on the available options.
Delayed Pressure Urticaria
Delayed pressure urticaria is a subtype of inducible urticaria different from all other forms of chronic urticaria. It is characterized by deep dermal, often painful swellings in the absence of wheals that appear after the skin is exposed to sustained pressure. Symptoms usually do not appear immediately, but several hours after exposure to the stimulus, which is different from other types of CIndU
Triggers
Swelllings are triggered by skin exposure to sustained pressure, including daily routine activities such as wearing shoes or tight clothing (affecting constricted areas), sitting on a hard surface, riding a bicycle, or standing for long periods, strenuous walking (affecting the soles), carrying heavy bags (affecting the palms, hands, shoulders), and compression against a pillow (affecting the face).
Testing
Diagnosis of delayed pressure urticaria can be made on the basis of patient history and the results of skin provocation testing. In clinical practise several types of tests are used. Common provocation testing methods include the “sandbag test” by applying a hanging weight on the shoulder, forearm, or thigh for 15 minutes or dermographic testing with a calibrated instrument.
Treatment
The treatment of delayed pressure urticaria includes the avoidance of described triggers and modification of triggers (e.g. broadening the straps of bags). Patients with delayed pressure urticaria should be aware that pressure is defined as force per area. Simple measures, such as broadening of the handle of heavy bags, may be helpful in preventing symptoms. In addition to avoiding the eliciting triggers as far as possible, pharmacological treatment (see treatment section) may be necessary to control symptoms (1).
Your doctor is the primary contact person to give you more information on the available options.
Heat Urticaria
Heat urticaria is a very rare type of CIndU characterized by the development of itchy wheals and/or angioedema after skin contact with heat (hot water or hot air) or a hot objects within minutes of exposure. Heat urticaria may present as immediate localized (immediate appearance of confined symptoms), immediate generalized (immediate appearance of symptoms beyond the heat-exposed area), or delayed localized (delayed appearance of confined symptoms) forms.
Triggers
Symptoms are triggered by exposure of skin to heat most commonly by warm objects, warm water, warm air (eg, hot wind, radiators, open fires), or solar thermal energy (eg, outdoor activities).
Testing
When sun exposure is reported as a trigger, heat urticaria should be differentiated from solar urticaria, especially when symptoms appear in the summer (involvement of sun-exposed/non-exposed areas). Diagnosis of heat urticaria can be made by heat provocation and threshold testing via applying a test tube of hot water on the skin for 4 to 5 minutes or a standardized Peltier element-based provocation device (TempTest®).
Treatment
Treatment of heat urticaria inlcudes the avoidance of described triggers. Emergency treatment should be available since heat urticaria bears a certain risk of systemic reactions.
In addition to avoiding the eliciting triggers as far as possible, pharmacological treatment (see treatment section) may be necessary to control symptoms (1).
Your doctor is the primary contact person to give you more information on the available options.
Vibratory Urticaria
Vibratory angioedema is a very rare type of CIndU It is characterized by the development of itchy wheals and/or angioedema within a few minutes at the site of skin exposure to vibratory stimuli.
Triggers
Triggers of vibratory angioedema preferentially comprise vibratory stimulation via walking/running and massages for the hereditary type and cycling, driving, and riding motorcycles for the acquired type.
Testing
Diagnosis can be made by vibration provocation testing. As a simple diagnostic tool, a vortex mixer may be applied on the skin (usually on the arm) for 10 minutes.
Treatment
Treatment of vibratory angioedema involves the avoidance of vibratory stimuli. In addition to avoiding eliciting triggers as far as possible, pharmacological treatment (see treatment section) may be necessary to control symptoms (1).
Your doctor is the primary contact person to give you more information on the available options.
Cholinergetic Urticaria
Cholinergic urticaria is a very frequent type of CIndU. It manifests with the appearance of characteristic tiny, short-lived itchy wheals with a pronounced flare and/or angioedema (although a rare symptom) triggered by an active or passive rise in body temperature induced by exercise, passive warming, emotional stress or spicy and hot food.
Triggers
Symptoms of cholinergic urticaria may be elicited by a rise in body temperatureassociated with e.g. exercise, sweating, hot baths, strong emotions, or spicy hot food.
Testing
A diagnosis of cholinergic urticaria is based on medical history and clinical presentation. Provocation and threshold testing to confirm the diagnosis may include pulse-controlled ergometry with moderate exercise. Cholinergic urticaria is frequently associated with atopic conditions and should be differentiated from exercise-induced urticaria, which is induced by exercise but not passive warming and is more often associated with systemic symptoms, and from exercise-induced anaphylaxis, a rare, but serious condition.
Treatment
Identification and avoidance of the triggers are crucial for managing cholinergic urticaria but may not always be possible.
Emergency treatment should be available since cholinergic urticaria bears a certain risk of systemic reactions. In addition to avoiding the eliciting triggers as far as possible, pharmacological treatment (see treatment section) may be necessary to control symptoms (1).
Your doctor is the primary contact person to give you more information on the available options.
Contact Urticaria
Contact urticaria is a very rare type of CIndU, characterized by the development of itchy wheals within minutes following direct contact of the skin with exogenous agents (e.g. plants, chemicals) at the site of contact(localized non-immunologic form) or spread beyond the contact site (generalized, immunologic form).
Triggers
Symptoms of contact urticaria can be elicited by many organic or inorganic substances such as latex, foods, plants, agents of animal origin, and chemicals.
Testing
Contact urticaria is diagnosed based on the patients’ history. The nature of potential triggering agent is assessed by appropriate cutaneous provocation tests like patchtest, pricktest or radioallergosorbent test (RAST) and may be accompanied by assessment of specific blood IgE antibodies.
Treatment
For the treatment of contact urticaria, avoidance of the eliciting triggers is advised. Emergency treatment should be available since contact urticaria bears a certain risk of systemic reactions. In addition to avoiding the eliciting triggers as far as possible, pharmacological treatment (see treatment section) may be necessary to control symptoms (1).
Your doctor is the primary contact person to give you more information on the available options.
Aquagenic Urticaria
Aquagenic urticaria is another rare type of CIndU characterized by the development of small itchy wheals within minutes following contact with the skin, mainly of the trunk. Symptoms occur regardless of the temperature of water.
Triggers
Most commonly aquagenic urticaria is triggered by tap water, but may also develop in response to saline or seawater.
Testing
Aquagenic urticaria is diagnosed based on the patients’ history and results of cutaneous provocation tests. A common provocation test can be done by applying a wet towel (soaked with 35-37°C water) to the trunk or known affected area for 5 minutes. The appearance of localized wheals within 10 minutes indicates a positive test and helps differentiate it from cold urticaria (triggered by cold liquids) and cholinergic urticaria (triggered by sweating). Differentiation of aquagenic urticaria from aquagenic pruritus, characterized by itch in the absence of wheals after contact with water is important, due to a reported association (in some cases) of aquagenic pruritus with lymphoproliferative disorders such as polycythemia vera and other myelodysplastic syndromes.
Treatment
Avoiding the eliciting trigger in aquagenic urticaria is only possible in certain cases depending on the type of water as the relevant eliciting agent. In addition to avoiding the eliciting triggers as far as possible, pharmacological treatment (see treatment section) may be necessary to control symptoms (1).
Your doctor is the primary contact person to give you more information on the available options.
Literature
(1) Zuberbier T, Abdul Latiff AH, Abuzakouk M, et al. The international EAACI/GA2LEN/EuroGuiDerm/APAAACI guideline for the definition, classification, diagnosis, and management of urticaria. Allergy. 2021; 77(3):734-766
Note on translations: If you are reading this website in a language other than English, it has been auto-translated to your language, unless otherwise stated at the bottom of each page. If you think the translation is inaccurate, please contact us, and we will be happy to review the translation.
