H. gammarus/ H. americanus commonly known as European/ American lobster is a decapod crustacean recognized worldwide by the consumption of its meat. The lobster allergen in present in its abdominal and tail muscle region. Shellfish allergy is more prevalent in Asian countries as compared to western countries due to its higher consumption. Children have a lower incidence of shellfish allergy than adults, where women are more prone as compared to men. Lobster allergy is primarily caused due to consumption of lobster meat and secondarily due to handling of lobsters and its products in sea food industry. Ingestion of lobster can lead to oral allergy symptoms followed by reactions on skin and sometimes lead to respiratory and anaphylactic reactions. Occupational contact dermatitis, rhinitis, asthma and conjunctivitis are also seen due to shellfish allergy. The best way to prevent any allergic reaction is to avoid the consumption of lobsters or may be the entire group of shellfish due to high rate of cross reactivity. Tropomyosin is the major allergenic protein present in shellfish. Tropomyosin is majorly responsible for cross reactivity among crustaceans, molluscs and arthropods.

Nature

European lobster or American Lobster (Homarus gammarus/ H. americanus) is a large, mobile decapod (10 footed). It feeds on a wide range of benthic invertebrates (1), such as blue mussels, hermit crabs and Polychaeta (2). The lobster has a chitin-containing exoskeleton. The exoskeleton consists of the epicuticle, exocuticle and endocuticle (3). European lobsters are bluish to bluish black dorsally along with white tracings on the carapace and abdomen. American lobsters are dark bluish green to brownish olive with dark greenish black spots (4). In the United States (US), lobsters are actively caught from July to November and are available fresh at that time whereas frozen lobsters are available throughout the year (5). Lobsters are known worldwide for the consumption of its meat and this can lead to a rising in allergic reactions in its consumers (6).

Habitat

Lobster is a benthic animal that lives on rocky substrates and feeds on prey (2). Seafloors with a steep slope and with medium to high wave energy conditions are the best places to find lobsters. Within waters, they are found at depths in the range of 35-40 m and also found at the boundary between sedimentary and rocky seafloors (7).

Taxonomy

Worldwide distribution

Shellfish allergy is one of the common food allergies which continues for a long time. Depending on the country and its dietary habits, the prevalence of shellfish allergy is reported to range from 1.3% to 5.2% (12). Shellfish allergy is more prevalent in Asian countries in comparison to western countries due to their higher consumption of shellfish (13). In the Philippines and Singapore shellfish allergy in teenagers was reported to be 5.12% and 5.23% respectively (14).

Furthermore, a study conducted on children residing in Singapore showed more prevalence of shellfish allergy in native children as compared to non-native children. In the age group of 4-6 years old, the prevalence rate was 1.19% for native children and 0.55% for non-native children. Similarly, in the age group of 14-16 years old, the prevalence rate was 5.23% for native children and 0.96% for non-native children (13).

In another study, conducted in Singapore by Thong et al. in 2018, on 120 participants (of mean age 19.1± 1.5 years), 64.2% reported having a food allergy from which shellfish was the most commonly reported food (78%) and among different shellfish, lobster was responsible for causing oral allergy syndrome in 3 % of the cases (15).

In a study in the USA, adults were found to have a higher incidence of shellfish allergy (2.8%) as compared to children (0.6%). And in addition, women had more incidence (3.6%) than men (2%) (14). A telephonic survey of 14,948 individuals in the US reported that 2-3% of the individuals claimed to have seafood allergy out of which 2.2 % was due to shellfish. Children (0.5%) estimated to have a lower allergy rate as compared to adults (2.5%). Shrimp was the most common cause of allergy followed by crab, lobster, clam, oyster, and mussel in the same decreasing order (13).

In Spain, epidemiological studies revealed a significant increase in shellfish allergy and became the third leading cause of allergic reactions to food with 85% reactions triggered by crustaceans (16).

In a South African study with 105 participants, it showed a severe reaction to seafood, almost 50% were found to be sensitized to lobster and shrimp (6).

In one study in Portugal with 840 adults, 34.6% of food allergic patients were found to be allergic to shellfish (17). 

Risk factors

Individuals who are in the vicinity of cooking shellfish by boiling, steaming or frying are prone to develop allergic reactions by inhalation of vapors (13). Fishermen, processing workers, shell grinders, cooks and even restaurant workers are at risk of developing allergic reactions to shellfish (18).

A person allergic to dust-mites can show an allergic reaction when exposed to lobsters (19).

Worldwide distribution

The European lobster is mainly found in the north-eastern Atlantic coast of Europe, between southern Norway and Portugal (20). The main production of lobsters takes place in the United Kingdom, Ireland and France. Major lobster meat consumption is seen in France, Spain and Italy (5, 7). In the US, the main markets for American lobsters are in Maine, Massachusetts and New York. Production of lobsters is carried out extensively in Canada as this country is the main supplier of lobsters for the US market (5).

Main

Consumption of lobster meat is the main route of exposure to the allergen (10).

Secondary

The handling of lobsters can lead to allergic symptoms in humans (13). Inhalation is another route of exposure. Workers working in the sea-food industry are exposed to air-borne shellfish particulate matter formed because of different processing activities such as filleting, freezing, cooking, smoking, drying which get suspended in the air as aerosols and can be inhaled (21).

Oral food allergy syndrome and anaphylaxis

Shellfish allergy is a hypersensitive disorder (14). On exposure to shellfish, IgE-mediated allergic reaction takes place that may involve single or multiple organs. These reactions seen may be immediate or late-phase with a delay of up to 8 hours after intake of food. Oral allergy symptoms include mouth and throat itching and swelling of the lip. These reactions are followed by reactions on the skin like urticaria (red and raised welts), periorbital angioedema, and skin redness (17).

Ingestion of lobster can also lead to respiratory and anaphylactic reactions (6). Shellfish is known to induce food-dependent exercise-induced anaphylaxis. It is important to consider if exercise was performed before an allergic response. Shellfish allergy has also proved to be the leading cause of food anaphylaxis in Hong Kong and Taiwan (14).

One study in Singapore detected oral allergy syndrome (OAS) and anaphylaxis symptoms due to different types of shellfish ingestion in 120 patients and compared the rate of OAS and anaphylaxis. Skin prick test was found to be positive for lobster with symptoms of OAS in 91.7% and anaphylaxis in 63.6% positive cases (15).

A 30- year old man, with a mild history of persistent asthma and allergy due to house dust mites and pollen showed symptoms of generalized urticaria, facial erythema and pharyngeal pruritus after eating lobster. But he tolerated other kinds of crustacean, molluscs, and fish (19).

Exposure of skin to the shellfish allergens takes place in occupational settings while handling and leads to urticaria or allergic contact dermatitis. There is a 3 to 11% prevalence of occupational contact dermatitis due to shellfish (13).

Allergic rhinitis

Lobster, shrimp and crab are also known to cause occupational dermatitis, rhinitis and conjunctivitis in fishermen and processing workers, cooks, restaurant workers (18). 

Asthma

Workers working in shellfish- processing factories are estimated to develop occupational asthma with a prevalence of 2-36% (13).

Prevention strategies

Avoidance

Avoidance is one of the most effective means for the prevention of an adverse reaction to food allergens. By avoiding direct ingestion of lobsters or indirect contact through skin or products containing lobsters, the allergic symptoms can be prevented.  Patients that are allergic to shellfish like shrimp and lobster have to avoid the entire group of shellfish due to high cross reactivity rates (22). Also, it is important to protect the consumer by accurate labeling of the food products to prevent a potential life threatening condition for allergic persons (10).

As the IgE- mediated allergies are long-lasting in nature, it is better that the patients would avoid the consumption of lobsters completely (6).

Allergenic molecules

Author: Turacoz Healthcare Solutions

Reviewer: Dr. Christian Fischer

Last reviewed: November  2020