Chronic idiopathic urticaria and post-traumatic stress disorder (PTSD): an under-recognized comorbidity.

A large body of literature supports the role of psychologic stress in urticaria; however, the comorbidity between chronic idiopathic urticaria (CIU) and post-traumatic stress disorder (PTSD), a classic stress-mediated syndrome, has received little attention. The underlying etiology of urticaria is not identifiable in about 70% of patients, possibly because of difficulties with identification of a direct cause-and-effect relationship between a potential causative factor and the onset of urticaria. The core features of PTSD (Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, Text Revision [DSMIV-TR]) that are important in urticaria include (1) autonomic nervous system reactivity and state of sympathetic hyperarousal that can manifest as CIU, and (2) the persistent re-experiencing of the traumatic events in PTSD, which can manifest as urticaria or angioedema, or both, affecting a previously traumatized body region (eg, urticarial wheals affecting the body region where the patient had been stabbed years earlier). The following features of PTSD make it difficult to use the cause-and-effect model for the determination of causation: (1) PTSD may first emerge years after the initial trauma and is classified as PTSD with Delayed Onset (DSMIV-TR); and (2) the traumatic triggers that precipitate the PTSD symptoms may be unique and idiosyncratic to the patient and not even qualify as stressful or traumatic by standard criteria (eg, precipitating events for the PTSD may include smell of a certain cologne that was used by the perpetrator or witnessing a scene in a movie that was reminiscent of the location where the abuse occurred). Finally, in PTSD with Delayed Onset, patients may not make a conscious association between their recurrent urticaria and their earlier traumas because they can develop classically conditioned associations between stimuli that are reminiscent of the original abuse situation and their somatic reactions such as urticaria. The clinician needs to be aware of these factors, because satisfactory resolution of the CIU may not occur without treatment of the PTSD. If the clinician suspects underlying PTSD, it is best to refer the patient to a qualified mental health professional, because detailed history taking about traumatic experiences alone can have an acute destabilizing effect and heighten PTSD symptoms in some patients.