Allergy

Chronic spontaneous urticaria and internal parasites – a systematic review

Kolkhir P, Balakirski G, Merk HF, Olisova O, Maurer M. Allergy 2016; 71(3): 308–322

The role and prevalence of parasites in chronic spontaneous urticaria

Parasite infections (PI) have been linked with chronic spontaneous urticaria (CSU), yet the prevalence rate and role of PI in the aetiology of CSU remain unclear. 1In a systematic review published in Allergy, Kolkhir and colleagues examined the literature for findings on comorbidity rates, and considered the relevance and possible pathomechanisms of CSU caused by PI. 1

A targeted literature search of PubMed and GoogleScholar databases revealed 66 studies which investigated either the prevalence of PI in CSU, the prevalence of PI in urticaria (including CSU) or the prevalence of urticaria (including CSU) in PI. 1

Prevalence

39 independent studies reported prevalence rates of PI in CSU which ranged from 0–75.4%. 1

Of these 39 studies, two-thirds reported PI rates of ≤10%.1 PI was not found in patients with CSU in 8 studies. 1

Although many studies did not define the type of parasite, the authors found the most prevalent PIs reported were:

• Blastocystis hominis
  
• Giardia spp.
  
• Giardia lamblia
  
• Entamoeba hystolytica
  
• Helminths.

The prevalence rates of PI in 13 studies of paediatric patients with CSU ranged from 0–37.8% (compared with 0–75.4% in 11 adult studies), with the most commonly reported parasites in children being Ascaris lumbricoides and Giardia spp. 1

Compared with healthy controls, patients with CSU were more likely to have protozoa, seropositivity to Toxocara canis, and – in comparison to both healthy and atopic controls – Anisakis simplex sensitisation. 1

Conversely, in patients with PI, the rates of comorbid urticaria ranged from 1–66.7% in 18 independent studies.1 In addition, compared with healthy controls, patients with Blastocystis hominis or Strongyloides stercoralis infection showed higher rates of urticaria. 1

Antiparasitic treatment

Over half of the studies analysed investigated the effect of treatment for PI on symptom improvements in patients with CSU (22/39; 21 studies of antiparasitic drugs, 1 study of fish-free diet).1 In total, 35.7% of patients with CSU treated with antiparasitic drugs responded to treatment (n=269). 1In terms of efficacy, 9 of 21 studies reported efficacy of ≥50% for parasitic drug treatment in patients with CSU, with a range of 0–100% across 21 studies. 1

Improvement in CSU symptoms after treatment with antiparasitic drugs was reported in 16 out of 21 studies. 1

However, 5 of the 21 studies report no improvement of CSU with antiparasitic drugs.1 In patients with undefined urticaria, results of 7 studies reported efficacy in the treatment of PI ranging from 78.6–100%. 1

Potential pathogenic mechanisms

The authors also discussed possible pathogenic mechanisms of CSU by PI, which may involve:

• Specific IgE
  
• Th2 cytokine scewing
  
• Eosinophils
  
• Complement activation
  
• Coagulation systems.

Conclusions

In light of their findings, the authors concluded that PI could be considered as a rare underlying cause of CSU. 1They proposed that PI can only be regarded as the underlying cause when antiparasitic treatment eliminates the PI and also leads to remission of CSU.1 The authors suggest that although CSU may be pathogenically related to PI, further studies are required to improve our understanding of the underlying pathomechanisms of both disorders. 1

Report on: Chronic spontaneous urticaria and internal parasites – a systematic review. Kolkhir P, Balakirski G, Merk HF, Olisova O, Maurer M. Allergy 2016; 71(3): 308–322.

Reference list

1. Kolkhir P, Balakirski G, Merk HF, Olisova O, Maurer M. Chronic spontaneous urticaria and internal parasites – a systematic review. Allergy 2016; 71(3): 308–322.