Types and Classification

Urticaria can have a wide spectrum of presentations and subtypes. Urticaria is differentiated based upon its duration, with acute urticaria lasting for less than 6 weeks and chronic urticaria lasting for a longer time. Acute urticaria is more frequent, affecting about 20% of all people during their lifetime.

Chronic urticaria can be further classified into spontaneous (where wheals appear out of the blue without the need for an external trigger) and inducible forms. Other factors like stress, medications, infections, and others can worsen symptoms; however, they are not necessary for symptoms to appear.

On the other hand, patients with chronic inducible urticaria only have wheals when exposed to a specific trigger. Chronic Inducible urticaria is divided into physical urticaria and non-physical urticaria. Physical urticaria constitutes the largest group of chronic inducible urticaria. It is induced by a physical stimulus on the skin such as pressure, cold, heat, light and vibration. The distribution of wheals is localized to the site exposed to the trigger.  The areas not exposed to the trigger are free of symptoms. The most common forms of inducible urticaria include symptomatic dermographism and cold urticaria. Cholinergic urticaria, contact urticaria and aquagenic urticaria are non-physical forms of chronic inducible urticaria. Cholinergic urticaria develops when wheals are brought about due to a rise in body temperature like a hot bath, exercise etc.
Chronic spontaneous urticaria constitutes the bulk of patients with chronic urticaria, while chronic inducible urticaria is less frequent. Patients with chronic spontaneous urticaria can also have associated inducible urticaria and vice versa.

Acute Urticaria

Acute urticaria is characterized by the sudden onset of wheals or angioedema, or both, with symptoms lasting for less than 6 weeks. The wheals are associated with itching or a burning sensation. The symptoms can be bothersome; however, in most cases resolve within a few days to weeks. The cause is not always clear; infections, medications, food can trigger symptoms. It is imperative to recognize the presence of associated symptoms like shortness of breath, difficulty swallowing, dizziness and seek emergency medical advice if present. If a specific trigger is identified, it is important to avoid the same.

TRIGGERS AND CAUSES

Acute urticaria can be triggered by infections like flu, medications like pain killers (Aspirin, Ibuprofen, Diclofenac), antibiotics. If an individual is allergic to a specific food, this can also trigger urticaria. If food or medication is suspected to be triggering urticaria, it is important to make a clear association between consumption of the culprit and the start of urticaria symptoms (usually within a few hours). Sometimes, no clear cause can be identified.

TESTING

In most cases, the cause can be identified by taking medical history itself, like in the case of urticaria triggered by infection or medications and requires no further testing. Further testing may be warranted if an allergic reaction to a culprit food is suspected to confirm the association.

TREATMENT

Acute urticaria usually resolves within a few days to weeks. Symptomatic treatment with antihistamines (allergy medications) helps control the appearance of wheals, itchiness, and angioedema. Higher doses of antihistamines and short courses of steroids may be indicated in some cases. Emergency medical advice should be sought in the presence of associated symptoms like shortness of breath, difficulty swallowing, dizziness. If a specific trigger is identified, it is essential to avoid the same in the future.

Chronic Spontaneous Urticaria (CSU)

Chronic spontaneous urticaria is characterized by spontaneous (out of the blue) occurrence of itchy wheals, angioedema, or both, daily or for most of the days of the week for more than 6 weeks. This type of urticaria can take months or several years to resolve. Chronic urticaria can be a nuisance with a significant effect on the quality of life; however, it is not life-threatening.

 

TRIGGERS AND CAUSES

Urticaria or hives occur secondary to the activation of certain cells in the body’s immune system known as mast cells. Mast cells are commonly present in the skin, gastrointestinal and respiratory tract. In chronic urticaria, mast cell activation in the skin is triggered by the production of antibodies against the body’s own substances. Chemicals present in the mast cells like histamines are released into the skin, which can cause irritation of nerve endings resulting in localized itching. In addition, blood vessels expand and leak fluid, leading to redness and swelling. Chronic spontaneous urticaria is almost never allergic in origin. Various factors can trigger or worsen symptoms but are not the cause of urticaria itself. These include infections, medications like pain killers (aspirin, diclofenac, ibuprofen), stress, food like histamine rich foods, food additives like preservatives, color etc. Food induced worsening of symptoms are due to intolerance, and food allergy is rarely a cause of chronic urticaria. In most cases, no underlying cause can be determined.

TESTING

The diagnosis of chronic urticaria is based on symptoms, and further testing is not usually warranted. Basic tests may be done to determine the nature of the disease, especially in the presence of associated systemic symptoms, to rule out severe allergic reactions/anaphylaxis. Allergy testing for food is not indicated in patients with chronic spontaneous urticaria unless history suggests the immediate onset and recurrence of symptoms after a particular food.

TREATMENT

There is no cure for chronic urticaria at the current time, but symptoms can be controlled in most patients. The main aim of treatment is complete control over symptoms. The main treatment for chronic urticaria are antihistamines which are anti-allergy medicines. Non- sedating antihistamines (2nd generation antihistamines) are recommended, and dosage can be increased up to a maximum of 4 times the dose if symptoms are not controlled on single dosing. Biologic agents like omalizumab or immunosuppressive medications are added if antihistamines do not relieve symptoms. Although corticosteroids may be used for a short time during severe flares, steroids should not be used for long. If specific triggers like medications or food are identified, these should be avoided.