**3. Delayed pressure urticaria (DPU)**

Delayed pressure urticaria (DPU) manifests with pink/red whealing or angioedema of the skin at sites of sustained pressure, such as tight clothing, walking, or sitting down. It is called delayed because hours (6–8 h) are necessary for it to manifest [9, 13]. The patients suffer from severe pain and burning sensation in contrast to other PUs. Fatigue and arthralgia can accom‐ pany. The quality of life is much more affected in DPU patients when compared with other forms of PU. Sometimes, the lesions can last up to 72 h [14].

The diversity of symptoms suggests that other mediators such as cytokines and interleukins play a role in addition to histamine in the pathogenesis of DPU. There is evidence that IL‐1, IL‐3, IL‐6, and tumor necrosis factor alpha (TNF‐α) play a role in the etiopathogenesis [12]. More recently, neuropeptides, such as substance P and calcitonin gene‐related peptide, have also shown to be taking a part in the formation of DPU [15].

After taking proper history of the patient, if there is a suspicion of DPU, skin provocation test should be performed. Either weighted rods (7 kg weight with a 3 cm wide strap over the shoulder) or dermographometer can be used for this purpose. Weighted rods should be applied for 15 min and the dermographometer for 70 sec. If a red‐colored edema appears after 6 h of the trigger, the test result is accepted as positive [16].

The etiology of DPU is not clear, so symptomatic treatment and avoidance are the mainstay of the therapy. Angioedema can be made less frequent or less severe with H1 antihistamines [3]. Most of the time, additional efforts are necessary to control the attacks. Leukotriene antago‐ nists, dapsone, sulfasalazine, or combinations of these have been reported to be successfully used in the literature. Systemic steroids can be used in flare‐ups. Recent studies show the benefit of omalizumab, but further controlled studies are necessary [17]. Anecdotal reports have shown the efficacy of intravenous immunoglobulins, tranexamic acid, and chloroquine [18, 19]. More recently, good results with gluten‐free diet have been reported [14]. Cassano et al. reported remission of DPU after eradication of Blastocystis hominis surprisingly [13].
