Contact urticaria (CU) is a hypersensitivity reaction, precipitated by dermal or mucosal contact with a trigger (urticariogen). Typically, only the area of the skin directly exposed to the urticariogen will display the symptoms commonly known as "wheal and flare reaction": edematous lesions (wheals) surrounded by erythema, usually with itching or burning sensation [1] [2] [3]. However, eczema covering the affected area might mask the symptoms and lead to under diagnoses. The main characteristic of CU is the rapid onset of symptoms, sometimes within minutes of contact with the inducing agent. After several hours (up to a day) symptoms regress spontaneously, leaving no residual effects. Depending on the time between the symptom flare-up and the physical examination, the patient may appear to be asymptomatic [1] [4].

The severity and distribution of symptoms may depend on etiology of CU. While non-immunologic CU (NICU) is usually limited to the exposed skin, some patients with immunologic CU (ICU) may develop generalized urticaria, rhino-ocular, respiratory, laryngeal or gastrointestinal symptoms and, in most severe cases, anaphylactic shock. Extracutaneous manifestations of CU are referred to as contact urticaria syndrome (CUS) [3] [5].

First exposure to an urticariogen can lead to NICU, whereas in ICU first contact results in sensitization with symptoms developing only on subsequent exposure [3]. Hence, patients may or may not associate a specific substance to the onset of CU.

Diagnosing CU starts with a detailed anamnesis, trying to identify the eliciting substance, followed by a physical examination. The next step involves cutaneous provocation tests, if necessary. Serology is rarely warranted and can be of use only in ICU.

Anamnesis

Given the variety of potential urticariogens, from cosmetics and foodstuffs to consumer goods (clothing, shoes, items containing latex), metals and industrial chemicals, virtually any substance can be suspected of precipitating CU [1] [6] [7]. Since occupational exposure is common, information about patients' workplace is highly relevant [3] [5]. Patient history includes the frequency, duration, severity and sites of urticaria occurrence in addition to personal and family history of atopy [1]. Use of antihistamines two days prior to cutaneous provocation tests should be excluded, to prevent false negative results [3].

Cutaneous provocation tests

Cutaneous tests compare the skin reaction upon contact with suspected urticariogens to positive and negative controls (e.g. saline and histamine hydrochloride, respectively) [1] [3]. Substances are conventionally applied to unaffected or slightly affected skin. Usually, treated areas are inspected periodically during an hour, starting at 15 minutes after application; wheals, edema or erythema denote a positive reaction. Due to variable sensitivity, various sites may be tested (forearm, upper arm, upper back), commonly starting with the one reported in patient history [1] [3] [8].

Initially, open application test is performed, by spreading each tested substance over a small, defined area [1] [3] [8]. In case of negative results, prick test can be used, where the skin is slightly pierced by a lancet subsequent to trigger-substance application [1] [3]. For non-standardized substances, scratch and chamber-scratch tests are the methods of choice [1] [3]. Use test is convenient for reactions triggered by consumer goods [3]. The possibility of anaphylaxis warrants caution in provocation tests [1].

Serology

Although not routinely used, radioallergosorbent test (RAST) for allergen-specific IgE antibodies may confirm the diagnosis of ICU [9].

The primary treatment for contact urticaria is avoidance of the triggering substance. Antihistamines are commonly used to relieve itching and swelling. In cases of severe reactions, corticosteroids may be prescribed. For systemic symptoms, such as difficulty breathing, immediate medical attention is necessary, and epinephrine may be administered.

The prognosis for contact urticaria is generally good, especially when the triggering substance is identified and avoided. Most reactions are self-limiting and resolve within a few hours to a day. However, repeated exposure can lead to more severe reactions, so it is important for patients to be aware of their triggers.

Contact urticaria can be caused by a wide range of substances, including foods, plants, chemicals, and medications. Common triggers include latex, certain foods like shellfish or nuts, and topical medications. The reaction can be immunologic, involving the immune system, or non-immunologic, where the reaction is due to direct irritation of the skin.

Contact urticaria is relatively common, though exact prevalence rates are not well-documented. It can affect individuals of any age, but certain occupations, such as healthcare workers or hairdressers, may have a higher risk due to frequent exposure to potential allergens. Both men and women are equally affected.

In immunologic contact urticaria, the body's immune system mistakenly identifies a harmless substance as a threat, leading to the release of histamines and other chemicals that cause the symptoms. In non-immunologic contact urticaria, the reaction is due to direct irritation of the skin cells, without involving the immune system.

Preventing contact urticaria involves identifying and avoiding known triggers. Patients should be educated on reading labels and recognizing potential allergens in their environment. Protective clothing or barriers may be used in occupational settings to reduce exposure. Regular skin care and moisturizing can also help maintain the skin's barrier function.

Contact urticaria is a skin condition characterized by rapid onset of hives following exposure to certain substances. Diagnosis is based on clinical history and testing, while treatment focuses on avoidance and symptom management. With proper identification and avoidance of triggers, the prognosis is generally favorable.

If you experience sudden itching, redness, or swelling after touching certain substances, you may have contact urticaria. It's important to note what you were exposed to before the reaction occurred. Avoiding these triggers is key to managing the condition. Over-the-counter antihistamines can help relieve symptoms, but if you experience severe reactions, seek medical attention immediately.

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