Key points
- Allergic reactions are caused by saliva allergens.
- LLR after bites of hematophagous insects occur in approximately 5% of
the general population.
- SSR are rare; the most frequently reported triggers are horse flies
and kissing bugs. Occasionally, SSR may occur after bites of
mosquitoes, tsetse, and louse flies. Mastocytosis may be a relevant
risk factor for SSR.
Diagnosis (see Table 5)
Diagnosis relies strongly on medical history. Clinical presentation of
skin lesions is, in itself, rarely diagnostic of a particular insect.
Flea and bedbug bites frequently display a characteristic pattern known
as “breakfast, lunch, and dinner”.128
Commercial extracts for skin testing and in vitro IgE
determination are available only for a very limited number of species.
They are, throughout, whole-body extracts with low sensitivity due to
small amounts of relevant saliva allergens.91,114,129They also have low specificity since they contain inhalant allergens
unrelated to insect bite hypersensitivity (e.g.
tropomyosin).91,129 Irrelevant IgE-binding may also
occur through CCDs.130 Several saliva allergens have
been expressed as recombinant proteins, yet none of them has become
commercially available for routine diagnosis.
The expected benefits of improved IgE diagnostics need to be clarified.
IgE testing may be decisive in hypersensitivity to insects rarely
causing sensitization but less so in, for example, mosquito allergy
where up to 80% of the general population show type 1
sensitization.85 IgE levels in “allergic” subjects
and those with “normal” skin reactions substantially overlap making
detection of discriminative cut-off levels
difficult.99,131 Significant morbidity in insect bite
hypersensitivity is linked with delayed cell-mediated large local
reactions where IgE-directed diagnostics may have limited value. Another
diagnostic problem is the large number and geographic variability of
relevant insect species and the uncertain cross-reactivity between them.