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.

• Mucosal Edema

  Histamine is released after allergen-bound IgE binds to mast cells, basophils, Langerhans cells, and eosinophils, ultimately leading to mucous secretion, airway smooth muscle contraction and mucosal edema. [dermatologyadvisor.com]

  […] of allergen-bound IgE to mast cells, basophils, Langerhans cells, and eosinophils, histamine (as well as leukotrienes and prostaglandins) are released.[11,12] These inflammatory mediators lead to mucus secretion, airway smooth muscle contraction, and mucosal [ncbi.nlm.nih.gov]

• Eczema

  OBJECTIVES: To identify factors associated with job change in a cohort of participants with recognised occupational hand eczema/contact urticaria METHODS: A registry-based study including 2703 employees with recognised occupational hand eczema/contact [ncbi.nlm.nih.gov]

  However, although the clinical picture and biopsy findings are consistent with eczema, patch testing is generally negative. [escholarship.org]

  There was no sign of eczema, nor a history of skin diseases or atopy in the patient or her family. [jamanetwork.com]

  Clinical Summary: A 25-year-old man (case 1) and an 18-year-old girl (case 2) with atopic dermatitis visited our Department because of food allergy and hand eczema. After starting their work with fish, severe itchy eczema appeared on their hands. [karger.com]

• Pruritic Rash

  Immediately, she developed oralaryngeal malaise and pruritic rash. Nasal obstruction and increase of cutaneous lesions were seen although she took betamethasone, 2 mg, orally. [scirp.org]

  Case reports of CU caused by local application of alcohol seem to be very rare, and include the following examples: a patient who noted a diffuse pruritic rash after drinking alcoholic beverages, with ethanol applied to the skin provoking an erythematous [onlinelibrary.wiley.com]

  Systemic symptoms including facial edema, nasal discharge, sneezing, pruritic rash, and mild dyspnea occurred in a 27-year-old female after the application of levofloxacin antibiotic eye drops [ 43 ]. [link.springer.com]

• Chronic Dermatitis

  TCS are widely accepted as the treatment of acute and chronic dermatitis and may be sufficient for localized lesions. The vehicle, however, is an important consideration. [worldallergy.org]

  Corticosteroids In the last decade, it has become clear that some individuals with chronic dermatitis develop allergy to topical corticosteroids. [emedicine.medscape.com]

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].

1. Gimenez-Arnau A, Maurer M, De La Cuadra J, Maibach H. Immediate contact skin reactions, an update of Contact Urticaria, Contact Urticaria Syndrome and Protein Contact Dermatitis -- "A Never Ending Story". European Journal of Dermatology. 2010;20(5):552-62.
2. Poonawalla T, Kelly B. Urticaria. American Journal of Clinical Dermatology. 2009;10(1):9-21.
3. Maibach H, Bhatia R, Alikhan A. Contact urticaria : Present scenario. Indian Journal of Dermatology. 2009;54(3):264.
4. Wakelin SH. Contact urticaria. Clinical and Experimental Dermatology. 2001;26(2):132-136.
5. Williams J, Lee A, Matheson M, Frowen K, Noonan A, Nixon R. Occupational contact urticaria: Australian data. British Journal of Dermatology. 2008;159(1):125-131.
6. Giménez-Arnau A, Silvestre JF, Mercader P, et al. Shoe contact dermatitis from dimethyl fumarate: clinical manifestations, patch test results, chemical analysis, and source of exposure. Contact Dermatitis. 2009;61(5):249-260.
7. Stingeni L, Neve D, Tondi V, Bacci M, Lisi P. Immunological contact urticaria caused by dimethyl fumarate. Contact Dermatitis. 2014;71(3):180-183.
8. Helaskoski E, Suojalehto H, Virtanen H, et al. Occupational asthma, rhinitis, and contact urticaria caused by oxidative hair dyes in hairdressers. Annals of Allergy, Asthma & Immunology. 2014;112(1):46-52.
9. Lernia VD, Albertini G, Bisighini G. Immunologic contact urticaria syndrome from raw rice. Contact Dermatitis. 1992;27(3):196-196.