Clinical Experience
IgE-mediated reactions
Hypersensitivity to Squid may induce symptoms of food allergy in sensitised individuals. In reports on Squid allergy, patients generally had immediate hypersensitivity reactions after eating Squid or inhaling vapours while cooking Squid (3, 8-9). In particular, anaphylactic reactions after consumption of Squid by patients sensitised to House dust mites have been reported several times (10). Serum-specific IgE to Squid has been measured in patients with atopic dermatitis (but the clinical significance was not determined by challenges) (11).
A difficulty in assessing early reports of hypersensitivity to Squid is that the species involved were not identified. The assumption can be inferred but not absolutely confirmed that the species are closely interrelated and that tropomyosin is a major allergen of Squid that results in high cross-reactivity. In fact, a patient with cutaneous symptoms who was sensitised to Loligo opalescens and not to Loligo pealei has been described (2).
Hypersensitivity to Squid may occur more commonly than indicated in the literature, considering that Squid is an important food in Japan, is used in other Asian dishes, and in recent times is commonly served in restaurants (8). Shellfish – and especially Cephalopoedae (Octopus, Squid) – is one of the most popular foods in Spain. Shellfish is one of the most frequent causes of food hypersensitivity in this population and is the leading cause of food hypersensitivity in patients over 5 years of age (6).
In 48 Spanish adults with crustacea allergy, the most frequent causes of symptoms were Shrimp (33 cases) and Squid (24 cases); the most frequently found symptoms were urticaria/angioedema (39 patients), asthma (18 patients), and rhinitis (14 patients). The authors suggested that shellfish hypersensitivity can occur within the same phylum and between different phyla, reflecting common epitopes, and that Squid, Octopus and Limpet extracts contain large amounts of heat-stable allergens. There was no significant difference between prick tests with raw and with cooked extract (6).
Among 142 adult patients sensitised to foods (out of 7698 patients visiting an outpatient clinic in the Canary Islands), 120 experienced clinical symptoms after consumption of 1 or more foods. Sensitisation to Squid was reported in 33 patients (12).
In 7 patients who had had symptoms highly suggestive of IgE-mediated reactions after ingesting Squid or inhaling vapours from cooking Squid, the symptoms reported were nasopharyngeal pruritus (3), rhinoconjunctivitis (4), asthma (4), nausea, vomiting or diarrhoea (3), and urticaria and angioedema (3). All had previously suffered from persistent rhinitis or asthma for years as a result of allergy to mites. In addition, 6 of the 7 patients had had symptoms after ingesting Shrimp. Skin-specific IgE tests were strongly positive for boiled Squid extract and for various commercial crustacean extracts. Only 2 had borderline responses to the raw Squid extract. Specific IgE antibodies against boiled extract and several crustacean extracts were demonstrated in all patients (3).
Anaphylactic reactions after consumption of Squid by patients sensitised to House dust mites have been reported several times. A 5-year-old boy allergic to House dust mites developed an angioneurotic oedema after eating Squid. Skin- and serum-specific IgE showed an allergy associated with both House dust mites and Squid. The labial test was strongly positive, with labial oedema, swelling, and intense itching. The author suggested that in light of the potential seriousness of anaphylactic reactions, parents of children allergic to House dust mites, along with the children themselves, should be made aware of the increased risk of allergies to Squid (11).
Possible exercise-induced anaphylaxis after eating both Shrimp and Squid was reported in a 13-year-old Japanese boy who was sensitised to Shrimp, Squid, Crab, Octopus, Clam, and Short-neck clam (13).
Allergic interstitial cystitis caused by Squid hypersensitivity has been reported (14-15).
Exposure to Squid in the work setting may result in sensitisation and occupational allergic disease (16). Occupational protein contact dermatitis was described in a 24-year-old female fishmonger who presented with progressive episodes of dermatitis of the hands and forearms for 2 months. Symptoms were associated with cleaning baby Squid, which resulted a few minutes after starting with itching and erythema of the anterior forearms, followed 2 days later with vesicles and maculopapular lesions. Skin-specific IgE tests with seafood other than cephalopods were negative. Skin-specific IgE with baby Squid (Loligo vulgaris) was positive, but negative to adult Squid of the same species, Pacific squid (Toradodes pacificus), and Octopus (Octopus vulgaris). Patch test was positive to baby Squid (17).
Contact urticaria from L. japonica was reported by a 22-year-old male cook. Every time he handled uncooked Squid, he developed erythema, oedema, and itching and burning on his hands. Symptoms started within 15 to 20 minutes of contact. An open challenge of fresh Squid applied to his forearm provoked a reaction within minutes. Serum- and skin-specific IgE directed to L. japonica was established (18).
Occupational allergic contact dermatitis from Squid (L. opalescens) was reported in an 18-year-old female, who developed eczema on her hands and forearms a month after starting work on cleaning frozen Squid. Her symptoms worsened during the week and improved on weekends. An open patch test was negative, but a closed patch test was positive at 2 and 4 days to L. opalescens, though not to L. pealei. Patch tests with the body, ink and tentacles of L. opalescens were positive at 2 and 4 days (2).
Other reactions
It may be useful to evaluate anglers for sensitisation to Squid, if they are found to be allergic to bait. This is suggested by a report on a keen angler, who used maggots as bait on weekends and suffered with rhinoconjunctivitis for years. He was found to be allergic to maggots and also sensitised to Squid and, to a lesser extent, to Prawns (19).