Lehrer et al. (1985) [1706] used crossed immunoelectrophoresis to show that of the 7 allergens detected from white shrimp, 5 cross-reacted with crayfish, 3 with lobster and 1 with crab extract. Two precipitins appear to be common crustacea allergens and were present in shrimp, crayfish, lobster and crab.

There is strong IgE cross-reactivity between all the crustacea. The most important allergen in these species is tropomyosin and DeWitt et al. (2004) [1536] reported that recombinant Pen a 1 bound 94% of the IgE from the 6 crustacea specific sera. As tropomyosin is strongly conserved in sequence with more than 99% identity amongst penaeoid shrimps and 92% identity between more distantly related crustacea such as a penaeoid shrimp (Farfantepenaeus aztecus) and a crab (Charybdis feriatus), allergy to crustacea is generally treated as a single allergy.

Reese et al. (1996) [1560] report that the extracts from crawfish (Procambarus clarkii), crab (Callinectes sapidus) and lobster (Panulirus argus) showed similar binding to IgE to Pen a 1.

However, Morgan et al. (1989) [1571] report that 1/16 subjects reacted only to white shrimp (Litopenaeus setiferus) extracts and 2/16 subjects to brown shrimp (Farfantepenaeus aztecus) extract alone. Greater differences might be predicted for less closely related crustacea.

Crustacea are eaten after cooking so that the resistance of the allergenicity of tropomyosins to heat may cause these to be more dominant. Similarly, the use of extracts from boiled shrimp may favour the identification of the highly conserved tropomyosins. It is possible that less heat stable allergens are more species specific and that reaction to allergens such as arginine kinase (Yu et al. 2003 [1542]) is dependent on both cooking conditions and species.

There is also IgE cross-reactivity between crustacea and insects, gastropods, bivalves and cephalopods (Lehrer & McCants (1985) [1575]; van Ree et al. 1996 [1609]; Leung et al 1999 [1557]; Goetz & Whisman, 2000 [1594]). This is believed to be due to allergenic tropomyosins. Fernandez et al. (2003) [1539] demonstrated IgE binding and SPT reactivity to shrimp in subjects sensitised by insect and mite allergens without prior exposure to shrimp.

In contrast to the observed cross-reactivity in IgE binding between arthropods and mollusks, clinical cross-reactivity is less common and some but not all crustacea allergics can tolerate mollusks (Leung et al (1996) [1557]; Ishiwara et al. 1998 [1584]; Ishiwara et al. 1998 [1582]).

As the allergens are likely to be similar, data on other shrimps is relevant to this entry. In particular, much of the early research is listed in the entry for white shrimp. As the species is often unspecified, data on "shrimps" is often repeated in several entries.

Rance et al. (2005) [1647] reported that 13 of 183 food allergic children were allergic to shrimp, showing that shrimp was responsible for 5.3% of food allergies in their population (7^th most common). As 2716 questionaires had been returned from children at a number of schools, this implied a prevalence of 0.48%. Osterballe et al (2005) [1764] reported that 3 adults and no children were allergic to shrimp by DBPCFC from their population of 898 children and 936 adults. Thus the adult prevalence of allergy to shrimp was 0.3%.

Morgan et al. (1989) [1570] reported SPT results with other foods for 36 patients with a history of shrimp allergy. The atopic patients with pulminary symptoms were also more likely to show other sensitizations.

Morgan et al. (1990) [1567] determined the levels of different classes of IgG antibodies to white shrimp extract in the sera of 31 DBPCFC positive patients. IgG1, IgG2 and IgG4 antibodies levels were higher in shrimp allergic individuals than in controls (significantly for IgG2 and IgG4). However, the IgG levels did not give useful diagnostic information. 

Sheah-Min & Choon-Kook (2001) [1547] similarly measured levels of IgE, IgG and IgG4 to shrimp and crab (using Bencard allergens) in allergic patients. The levels of these antibodies did not correspond with each other. High IgE or IgG4 levels were significantly associated with allergy. IgE levels were most predictive of allergy but were not a reliable test for allergy.

Crustacea have been frequently reported as occupational allergens. Several species in addition to those mentioned in articles on food allergy have been reported as occupational allergens including snow crabs (Cartier et al, 1986 [1591]; Cartier et al, 2004 [1610]), Nephrops norvegicus or scampi (Griffin et al, 2001 [1611]) and gammarus shrimps (Fontan et al. 2005 [1765]; Baur et al. 2000 [1550]). Occupational allergy probably involves aerosols (Bang et al. 2005 [1767]; Goetz & Whisman, 2000 [1594]; Desjardins et al 1995 [1561]) and both the stability of tropomyosins in boiling water (Lehrer et al. 1990 [1607]) and their cross-reactivity may be significant. Other allergens such as the 97 kDa allergen of scampi are also stable as aerosols (Griffin et al, 2001 [1611]). However, contact determatis has also been reported (Aasmoe et al, 2005 [1766]; Scharer et al, 2002 [1612]).

Shellfish can act as hidden allergens in fishcake made from finfish and Faeste et al. (2003) [1616] report a case of anaphylaxis with detection of IgE against shrimp tropomyosin and also detection of (invertebrate) tropomyosin in the fish cake.

Apparent allergy to shellfish can arise from allergy to parasitic worms (Gonzalez-Galan et al. 2002 [1388]).