**1. Introduction**

Urticaria, also known as hives, is a common, mast cell‐driven, itchy condition which is char‐ acterized by red/pink, swollen whealing of the skin [1]. The lesions can vary from a few mil‐ limeters to tens of centimeters. Chronic urticaria is defined when the transient lesions that disappear in <24 h and last more than 6 weeks in repetitive manner [2]. Most of the chronic urticaria cases are idiopathic [3]. Chronic spontaneous urticaria is the spontaneous appear‐ ance of wheals, angioedema or both due to known or unknown causes for a period longer than 6 weeks. In case of a known trigger that causes whealing, angioedema or both at every exposure, chronic inducible urticaria term is used. Chronic inducible urticarias consist of physical urticarias (PUs) and cholinergic urticaria (CU) [1, 3, 4]. **Figure 1** demonstrates the classification of urticaria according to EAACI/GA<sup>2</sup> LEN/WAO 2013 guideline.

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**Figure 1.** Classification of urticaria, according to EAACI/GA2LEN/WAO 2013 guideline.

Physical urticaria (PU) is a subgroup of acquired, chronic inducible urticaria which is associ‐ ated with a known physical trigger [5]. In PU, the symptoms are induced by exogenous physi‐ cal triggers such as friction, pressure, vibration, cold, heat or solar radiation. All the PUs may manifest with both wheals and angioedema at the sites of the triggers with the exceptions that urticaria factitia (symptomatic dermographism) presents with wheals only and pressure urticaria presents with angioedema only [6, 7]. **Table 1** summarizes the types and subtypes of chronic inducible urticaria and the triggering agents.

Cholinergic urticaria is another subtype of inducible urticaria. Because of the fact that the symptoms are not triggered by exogenous physical exposure, cholinergic urticaria is not con‐ sidered as PU. Rather, it is induced by an increase in the body core temperature [8].

Almost 0.5% of the population suffers from chronic inducible urticaria that makes nearly 15–25% of all chronic urticarias [7]. All forms of urticaria do not only cause impaired quality of


**Table 1.** Classification of chronic inducible urticaria.

life but also affect performance at social life, school and work [9]. PU is classified depending on the type of the physical trigger. They are diagnosed by using different provocation tests induc‐ ing wheals and sometimes angioedema [3]. It is important to make provocation tests after tak‐ ing the patient's history in order to get a proper diagnosis. One must be very careful during the provocation tests as systemic symptoms including shock can develop along the course [10]. In chronic inducible urticaria, the threshold of the causative trigger must be established to assess the severity of the condition. These threshold levels also allow us to evaluate the activity of the diseases and the response to the therapy [11]. PU generally accompanies other forms of chronic urticaria such as spontaneous urticaria and/or other inducible urticaria types. Therefore, every patient with one of the PUs must be tested with all physical triggers that seem to be relevant from the medical history [12]. The result of the provocation test changes according to the medi‐ cal status of the patient. That's why the test should be done prior to the treatment if possible. Testing should be performed on skin areas which have not been complicated with wheals recently. Because affected skin areas exhibit a refractory period after urticarial reactions. In case of a negative result despite a strong suspicion, the testing can be repeated several times. In cholinergic urticaria, the patient must be asymptomatic for 48 h before testing [6].
