Food allergy in Sri Lanka – A comparative study

Abstract

Background

The incidence of IgE mediated food allergy (FA) is increasing in the west. Cow's milk (CM), hen's egg, wheat, soy, peanut, tree nut, fish, and shellfish are responsible for 90% of food allergy in the west; however, local dietary habits may result in specific allergies. Data on food allergies in South Asia is scarce. The present study aims to evaluate the foods that cause immediate type hypersensitivity in Sri Lanka, and to compare with Asia and the developed west.

Methods

Records of patients referred to an Immunology clinic from 2010–January 2022 were reviewed. The diagnosis of food allergy was based on standard guidelines. Confirmation of the specific food implicated was based on the history and the presence of specific IgE or component resolved diagnostics by in vitro methods (Phadia ImmunoCap) or by skin prick testing with commercial extracts (Alk Abello). Prick to prick testing was performed for fruits and vegetables when commercial extracts were unavailable.

Results

Three hundred and forty-six patients were confirmed with food allergy. CM allergy (CMA) was the commonest (31.2%) followed by red meat allergy (27.7%) and food dependent exercise induced anaphylaxis (FDEIA) (17.9%). Allergy to alpha-gal crustaceans, eggs, gelatin, wheat, coconut milk, and mollusks were seen in 2–10% of patients.

The onset of CMA was mainly in childhood. However, in 23/108 patients, onset was after 5 years, including 8 patients in adulthood, and in 14 of the 23, it was preceded by red meat allergy. Onset of primary red meat allergy was predominantly in children, but in 33/96 (34.3%) of patients, it was in adults. Most patients with alpha-gal allergy (21/29, 72.4%) had initial symptoms in childhood and adolescence.

Anaphylaxis was diagnosed in 213 patients. FDEIA is the commonest cause (24.7%) followed by red meat allergy (23%), CMA (21.5%) and alpha-gal allergy (10.3%). Allergy to peanuts and fruits were rare.

Patients with red meat allergy and/or CMA developed allergy, including anaphylaxis, to vaccines containing bovine/porcine products.

Conclusion

CM was the most common food allergy in children, but egg allergy was uncommon. Primary red meat allergy was the second most common, and was associated with allergy to vaccines containing bovine products, such as the measles, mumps and rubella (MMR) vaccine. Allergy to peanuts and fruits were rare. Primary red meat allergy may be responsible for late onset CMA.

Introduction

Food allergy is “an adverse health effect arising from a specific immune response that occurs reproducibly on exposure to a given food”.¹ In contrast, non-allergic adverse reactions to foods may be the result of food intolerances or adverse physiologic reactions.¹ IgE mediated food allergies are the best characterized of food allergies, whose incidence is increasing in the west. IgE mediated food allergy may give rise to cutaneous (urticaria, angioedema), gastro intestinal (vomiting, diarrhoea and abdominal pain), cardiovascular (hypotension), and respiratory (oral allergy syndrome, stridor, wheeze, cough) symptoms and signs. Some of these patients will have anaphylaxis. Cow's milk (CM), egg, wheat, soy, peanut, tree nut, fish, and shellfish are responsible for 90% of food allergy in the west;² however, local dietary habits may result in specific allergies, for example, sesame in Israel and buckwheat in Japan.³

In East and Central Asian countries, the food triggers for severe allergic reactions are major components of the Asian diet: fish, shellfish, bird's nest, buckwheat, and royal jelly.⁴ In Singapore, Thailand, and Hong Kong, shellfish is one of the most important food triggers of anaphylaxis in adults and children. Allergy to edible bird's nest from swiftlets has also been described in Singapore and Malaysia.⁴

Data on food allergies in South Asia are scarce. In the EuroPrevall-INCO study conducted in 8 countries, the incidence of food allergy in adults in India was 1.3% with CM and apple being the commonest food allergens.⁵ A meta-analysis showed the food allergens identified in India; Apple, fish, banana, cow's milk, melon, sesame, shrimp, tree nuts, chickpea, capsicum, Indian lentils, avocado, banana, beef, bulgur wheat, coconut, corn, eggplant, garlic, ginger, green peas, jalapeño peppers, kiwi, melon, rice, and tomato.⁶ In addition, there are a few case reports of allergy to mango, mushroom, fenugreek, and chickpea.⁵

The data from Sri Lanka is meagre. Using a questionnaire in 449 school children in the Colombo District, 30% of the respondents believed they had a food allergy, of which pineapple was thought to be the commonest allergic food. In addition, rambutan (Nephelium lappaceum), tomato, bread fruit (Artocarpus altilis), prawns, cuttle fish, tuna, and canned fish were implicated.⁷ However, confirmatory tests were not performed.

Anaphylaxis is the most dangerous allergic manifestation. In a global review on food-based anaphylaxis,⁸ the commonest foods implicated were peanut, sesame, eggs, CM, celery, lupin, tree nuts, wheat, crustaceans, mollusks, fish, soy, and fruits. Other animal foods were also implicated. However, in Sri Lanka, CM (26%), eggs (2%), sesame (2%), spices other than sesame (2%), wheat (3%), crustaceans (4%), mollusks (1%), and fish (2%) were responsible for anaphylaxis.⁹ Anaphylaxis to red meats were seen in 40% of patients in Sri Lanka, much more than in other countries.

Two novel food allergies have been identified in the past 2 decades, both leading to anaphylaxis. Food-dependent exercise-induced anaphylaxis (FDEIA) occurs when physical exertion follows ingestion of the implicated food, generally within 4 hours. While many foods have been implicated, wheat is responsible for FDEIA in Sri Lanka.¹⁰ Alpha gal allergy is responsible for allergy to red meats. A tick bite sensitizes a patient to a carbohydrate moiety (alpha gal), which is present in the saliva of ticks and in non-primate mammals.¹¹ Ingestion of red meat leads to delayed anaphylaxis (up to 7 hours after ingestion). While this condition has not been reported so far in Sri Lanka, we have identified a number of such persons.

The present study aims to evaluate the foods that cause immediate type hypersensitivity, and to compare with data from Asia and the west.

Methods

Our immunology clinic in Sri Lanka caters to patients from the entire country. Patients with allergy are investigated and treated in the clinic. In this retrospective study, the clinic records from 2010–January 2022, a period of 12 years, were evaluated for probable allergy. Patients who had clinical features suggestive of immediate hypersensitivity, reproducibility between specific food ingestion and symptom(s) occurrence, and confirmation of the relevant food by detection of food allergen-specific IgE, were selected. Patients who did not participate in testing, and those with food allergy leading to asthma or atopic dermatitis, and where a food allergen could not be identified, were excluded. The diagnosis of anaphylaxis was based on the clinical history and examination findings as noted in the diagnosis card or bed head ticket. The diagnostic criteria included one of 3 clinical scenarios; namely, (1) acute onset of skin manifestations associated with respiratory or cardiovascular signs or symptoms, (2) involvement of at least 2 systems (skin, respiratory, cardiovascular, or gastrointestinal) that occurred rapidly after exposure to a likely allergen for that patient, or (3) reduced blood pressure after exposure to a known allergen for that patient.¹² The diagnosis of food allergy was based on standard guidelines.¹² Patients with a history of food allergy within 2 hours of ingestion were selected. The food allergy (FA) included oral allergy syndrome, acute urticaria/angioedema, rhino-conjunctivitis/asthma, gastrointestinal symptoms, anaphylaxis, and FDEIA. Confirmation of the specific food implicated was based on the history and the presence of IgE to the implicated food, by the presence of specific IgE (by Phadia ImmunoCap, using a Phadia 100), or by skin prick testing with commercial extracts (ALK Abello). In vitro allergens included the following; cow's milk, beef/pork, bovine gelatin, shrimp, cuttle fish, egg white and egg yolk, wheat, peanut, coconut, lentil, sesame seed, soy bean, tuna, salmon, mackerel, yeast, and tomato. Skin prick reagents included cow's milk, beef/pork/mutton, egg (whole/white/yolk), coconut, lentils, almond, brazil, cashew and hazel nuts, shrimp, cuttle-fish, pineapple, banana, and melon. Where commercial extracts or in vitro diagnostics were not available, as for example, fruits and vegetables, prick to prick testing was performed. Component resolved diagnostics (CRD) were performed with reagents from Phadia ImmunoCap.¹³ These include rTri a 19 omega-5 gliadin, nGal d 1 ovomucoid, nGal d 2 ovalbumin, nBos d 4 alpha-lactalbumin, nBos d 5 beta-lactoglobulin, nBos d 8 casein, nBos d 6 BSA, and nGal-alpha-1,3-Gal (alpha-Gal).

Alpha-gal allergy was diagnosed when there was a delayed onset of symptoms of up to 6 hours after ingestion of red meat with or without a history of tick bite.¹¹ Diagnosis was confirmed if IgE to alpha gal >0.35 kUA/L, IgE to alpha-gal > IgE to beef/pork,¹⁴ and IgE to bovine serum albumin (Bos d 6) was negative.¹¹ Primary red meat allergy was diagnosed where symptoms appeared within 2 hours of ingestion, and IgE to beef/pork or skin prick testing with commercial extracts were positive. Patients with positive results were analyzed with component resolved diagnostics, including IgE to Bos d 6 (bovine serum albumin, BSA) and bovine gelatin.

FDEIA was identified when symptoms and signs of allergy, including anaphylaxis, occurred during or within an hour of exercise, preceded by ingestion of food (for up to 4 hours), or by ingestion immediately after exertion.¹⁵ People who developed allergy to the food in the absence of exertion, or with exercise unaccompanied by ingestion of the food, were excluded. The diagnosis was confirmed by testing for IgE to the culprit food. IgE to omega 5 gliadin was done in patients where the implicated food was wheat. Due to safety issues, challenge testing was not done.¹⁵

Results

A total of 1255 patients attending the allergy clinic were evaluated for possible food allergy (FA), of whom 346 (27.5%) patients were diagnosed with immediate FA (Table 1). Seventy-three (21.09%) had allergy to multiple foods. Cow's milk allergy (CMA) was the commonest allergen diagnosed in 31.2% of patients followed by red meat allergy (27.7%) and FDEIA in 17.9%. Galactose-alpha-1,3-galactose (alpha-gal) allergy, and allergy to crustaceans, egg, gelatin, wheat, coconut milk, and mollusks were seen in 2–10% of patients. Most other allergies were seen in <1% of patients. These include peanuts, jambu, pecan/walnut, spinach, horse purslane (sarana, Trianthema portulacastrum), moringa (Moringa oleifera), and jackfruit (Artocarpus heterophyllus).

Table 1.

Patients’ ages at onset of different food allergies

Food Allergen	Number of patients (n = 346)a
	Age at onset						Total (%)
	0–6 months	6–12 months	1–5 years	5–12 years	12–18 years	>18 years
Cow's Milkb	38	29	18	13	2	8	108 (31.2)
Red meatb	0	5	16	33	9	33	96 (27.7)
Beef	0	3	9	21	5	23	61 (17.6)
Pork	0	2	8	17	7	12	46 (13.3)
Mutton	0	2	3	3	2	4	14 (4)
Venision	0	0	2	2	0	0	4 (1.2)
Others (Camel, Rabbit, Wild boar)	0	0	0	3	0	0	3 (0.9)
FDEIA	0	1	0	20	13	28	62 (17.9)
Alpha- Gal	0	0	8	11	2	8	29 (8.4)
Crustaceans	0	0	4	3	5	11	23 (6.6)
Prawns	0	0	4	2	3	10	19 (5.5)
Crabs	0	0	0	1	1	4	6 (1.7)
Shrimp	0	0	0	0	1	2	3 (0.9)
Egg	0	15	2	1	0	0	18 (5.2)
Gelatin	0	1	5	3	2	2	13 (3.8)
Wheat	0	1	1	1	1	6	10 (2.9)
Coconut	1	4	5	0	0	0	10 (2.9)
Mollusks	0	0	1	1	1	4	7 (2)
Cuttlefish	0	0	1	1	1	4	7 (2)
Fish	0	0	0	0	0	3	3 (0.9)
Sesame	0	0	2	0	0	1	3 (0.9)
Other foods (Peanuts, jambu, soy, lentils/legumes mushroom, pecan/walnut, banana, mango, spinach, horse purslane/ sarana (Trianthema portulacastrum), moringa (Moringa oleifera), jackfruit (Artocarpus heterophyllus), tomato)	0	2	6	2	0	7	17 (4.9)

^aSome patients had reacted to more than one food allergen.

^bCM allergy was also present in 9.3% of patients with beef allergy and beef allergy was present in 15% of patients with CMA

The onset of CMA was mainly in childhood. However, the onset of CMA in 10/108 patients (9.2%) was at 12 years or later, 8 patients developing symptoms after 18 years. Thirty-three patients with CMA had red meat allergy (30.6%). Of the 67 patients with CMA in infancy, only 6 had red meat allergy, which developed after CMA, whereas of the 23 patients who developed CMA after 5 years, 16 had red meat allergy, of whom 14/23 (60.9%) developed CMA after read meat allergy (Table 2).

Table 2.

Red meat allergy in patients with cow's milk allergy (CMA)

Age	Onset of CMA (n = 108)	Red meat allergy	Onset of red meat allergy before CMA	Onset of red meat allergy after CMA
0–6 months	38	2	0	2
6–12 months	29	4	0	4
1–5 years	18	10	4	6
5–12 years	13	9	7	2
12–18 years	2	1	1	0
>18 years	8	6	6	0

One hundred and twenty-five patients had allergy to red meats, of whom 96 (76.8%) were considered as having primary red meat allergy. The onset in the majority of patients with primary red meat allergy was in childhood. However, in 33/96 (34.3%), it was in adulthood (>18 years) (Table 1). Thirty-three patients with primary beef allergy (33.3%) had CMA.

Patients with a delayed onset (2–6 hours) were diagnosed with alpha-gal syndrome. Most patients with alpha-gal allergy (21/29, 72.4%) had initial symptoms in childhood and adolescence. Eight of 29 (27.5%) patients gave a history of tick bite within the previous year; however, the identity of the tick is not known.

Almost half of patients (11/23, 47.8%) allergic to crustaceans had initial symptoms in adulthood.

Anaphylaxis was diagnosed in 213 patients (Table 3). FDEIA is the commonest cause detected in 24.7% of patients and wheat was the only food implicated. Menstruation, taking non-steroidal anti-inflammatory drugs and inhalation of cannabis were cofactors in one patient each. The other major causes of anaphylaxis were primary red meat allergy (23%), CMA (21.5%), and alpha-gal allergy (10.3%).

Table 3.

Patients’ ages at onset of anaphylaxis to different food

Cause of anaphylaxis	Number of patients with anaphylaxis (n = 213)a
	Age at onset						Total
	0–6 months	6–12 months	1–5 years	5–12 years	12–18 years	>18 years
FDEIAb	0	0	0	19	11	27	57 (26.7)
Red meat	0	1	8	21	4	15	49 (23.0)
Beef	0	0	4	14	2	10	30 (14.0)
Pork	0	0	5	8	3	7	23 (10.7)
Mutton	0	1	2	1	1	1	6 (2.8)
Venison	0	0	1	0	0	0	1 (0.4)
Others (camel, rabbit, wild boar)	0	0	0	2	0	0	2 (0.9)
Cow's Milk	15	9	10	7	2	3	46 (21.5)
Alpha- Gal	0	0	5	9	1	7	22 (10.3)
Crustaceans	0	0	0	1	2	6	9 (3.9)
Prawns	0	0	0	1	1	6	8 (3.7)
Crabs	0	0	0	1	1	1	3 (1.4)
Shrimp	0	0	0	0	1	2	3 (1.4)
Gelatin	0	0	3	3	1	0	7 (3.2)
Coconut	1	4	2	0	0	0	7 (3.2)
Wheat	0	1	1	0	0	4	6 (2.8)
Mollusks	0	0	0	0	0	4	4 (1.7)
Cuttlefish	0	0	0	0	0	4	4 (1.7)
Egg	0	3	0	0	0	0	3 (1.4)
Fish	0	0	0	0	0	3	3 (1.4)
Other foods	0	1	4	1	0	8	14 (6.6)
TOTAL	16	19	33	61	21	77	213

^aSome patients had anaphylaxis to more than one food allergen.

^bFood Dependent Exercise Induced Anaphylaxis

In adults the commonest cause of anaphylaxis was FDEIA (47.3%), followed by primary red meat (30.6%) and alpha–gal (31.8%) (Table 3). Anaphylaxis to crustaceans, wheat, and fish were also seen.

CM was the commonest cause of anaphylaxis in infancy (68.5%) followed by coconut milk (14.2%) and eggs (8.5%). CM was also the commonest cause (30.3%) in children aged 1–5 years followed by red meats (24.2%) and alpha-gal (15.1%) Primary red meat allergy was the commonest cause of anaphylaxis from 5 to 12 years (34.4%) along with FDEIA (31.1%). FDEIA was the commonest cause from 12 to 18 years (52.3%).

Patients with red meat allergy and/or CMA developed allergy, including anaphylaxis, to vaccines containing bovine/porcine products (Table 4).

Table 4.

Patients with allergy to both food (red meat, cow's milk, gelatin) and vaccines

Vaccine	Food Allergy				Total (n = 40)
	Red meat	Cow's milk	Red meat + Cow's milk	Cow's milk + Gelatin
MMRa	4	9	5	1	19
MRb	0	0	1	0	1
Measles	1	0	2	0	3
Rubella	0	0	2	2	4
JEc	1	1	4	0	6
aTdd	0	0	1	1	2
DTe	0	2	1	1	4
ARVf	1	0	0	0	1

^aMeasles, Mumps and Rubella.

^bMeasles-Rubella.

^cJapanese Encephalitis.

^dAdult Tetanus diptheria

^eDiptheria Tetanus.

^fAnti-Rabies Vaccine

Rare causes included anaphylaxis due to ingestion of horse purslane (Trianthema portulacastrum), locally known as "Sarana", identified in 1 patient. In addition, anaphylaxis was rarely seen with to sesame peanuts, lentils, soy, jambu, banana, mango, spinach, moringa, jackfruit, and tomato.

Discussion

The pattern of food allergy depends on the feeding patterns of each country.⁴ The pattern of food allergies in Asia are different compared to the western developed world.¹⁶ However, the pattern of food allergy seen in our study has important differences with other Asian countries as well as with Europe and the United States (Table 5).^5,17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36

Table 5.

Comparison of food allergy in Sri Lanka with countries in Asia, Europe and USA^a

Sri Lanka	Thailand	Korea	China	Hong Kong24	Taiwan25	Singapore	Japan28	Vietnam		India	US	Europe
<1 year CM,Hen's egg	<1 years17Hen's egg CM,Soya	0–2 years19 CM,Hen's egg	0–2 year22Seafood,Fruits CM,Hen”s egg			1 year26Hen's egg CM	<1yearHen's egg CMWheat			<15 years31BananaEggBrinjalWheatLady's finger CM	0–5 years31 CMPeanutHen's egg
1–5 years CM,Red meat,Alpha gal,Gelatin,Coconut,Crustaceans		0–6 years20Hen's egg,Peanut,Soya,Fruits,Tree nuts,Crustaceans	0–7 years23Shrimp,Crabs,Mango, CM,Hen's egg			18 months26Hen's eggShellfish24 months26Hen's egg36 months26ShellfishHen's egg48 months26ShellfishHen's egg	1 yearHen's eggFish roe CMPeanutsFruits
				6–11 yearsShrimpFish/Hen's egg/crabs	3 yearsShrimpFishCrabs		2–3 yearsFish roeHen's eggPeanutTree nutFruits	Hue2–6 years29	Tien Giang2–6 years29			6–10 years34Iceland, UK, Germany, Spain, Poland-CMHen's eggPeanutThe Netherlands- CMHen's eggGreece-CM
								ShrimpFishHen's eggMollusksCM	ShrimpBeefMollusksFish
	3–7 years18CM,Hen's eggs,Shrimp	3–6 years19Walnut,Hen's egg,CM	3–5 years22Fruits,Seafood		4–18 yearsShrimpCrabsFishMangoMollusksCMPeanutHen's egg		4–6 yearsFruitsHen's eggPeanutBuckwheat/fish roe			6–11 years24Very low prevalence of FA	6–10 years32PeanutsCM	7–10 years35Poland, The Netherlands,Spain, Iceland, Lithuania, Greece, SwitzerlandHazelnutPeanutApplePeachKiwiCarrotSpain, Iceland ShrimpFishGreeceFish
5–12 yearsRed meatFDEIA (wheat)CMAlpha gal			6–14 years21Fruits,Seafood6 – 1124 yearsShrimp,				7–19 yearsCrustaceansFruitsHen's egg/wheatBuckwheat				11–13 years32PeanutsCMShellfish
12–18 yearsRed meatFDEIA (wheat)CMAlpha gal
>18 yearsRed meatFDEIA (wheat)Crustaceans		Adults21Pollen food allergy syndrome CrustaceansWheatBuckwheat Peanut Walnut Alpha Gal			>18yearsCM/ShrimpCrabsMollusksMangoPeanut	Adults27ShrimpCrabsMolluscs	>20 yearsWheatFishCrustaceansFruits	16–50 years30CrustaceansFishMollusksBeefEggCM		15–40 years31BananaBrinjalLady's figureTomatoWheat	Adults33Shellfish, CMPeanutsTree nutsFinfish
										20–54 years5CMApple
										>40 years13BananaBrinjalHen's eggTomato		Adults36Switzerland, Poland, The NetherlandsHazelnutApplePeachSpainPeachMelonShrimp

^aThe foods are displaced in descending order of prevalence

Cow's milk allergy (CMA) was the commonest food allergy in childhood in our population. CMA is one of the commonest food allergies among young children throughout Asia^{16,17,19,22,28} and high levels are also seen in Europe and United States.^3,32,34 A substantial proportion of our patients had an onset after 5 years, and in adulthood. These patients had developed red meat allergy before onset of CMA (Table 2) which may have predisposed to subsequent development of CMA. BSA may be responsible for the cross-reactivity.³⁷ Convincing data have emerged that CMA may manifest in adult life,³⁸ and further studies on the underlying mechanisms are warranted.³⁹

Allergy to red meats come in 3 different forms; primary red meat allergy, alpha-gal allergy, and pork cat syndrome. Only primary red meat and alpha-gal allergy were identified among our patients. Primary red meat allergy is the second most common food allergy in our patients. This is unusual, as, due to cultural and religious reasons, consumption of red meat is low. Red meat allergy, while uncommon, is identified mainly in children in other countries,¹¹ whereas in 34.3% of our patients, the onset was in those over 18 years.

Twenty-nine patients were diagnosed with alpha-gal allergy. In a previous paper from our group, alpha -gal allergy was not detected.⁹ To our knowledge, these are the first reported cases from the Indian subcontinent. None of the patients with immediate reactions (within 2 hours) to red meat were tested for IgE to alpha-gal due to financial constraints. Some of these patients may have had alpha-gal allergy. This is a limitation in our study.

Egg allergy was relatively uncommon in our patients, after infancy, unlike in Asia,¹⁶ Europe, and United States.¹⁶ For example, egg allergy predominates over CMA among children below 5 years in Korea,²⁰ Singapore,²⁶ and Japan.²⁸ However, the prevalence of egg allergy in Asia is lower than in the developed west.¹⁶

Shellfish allergy was seen in 6.6% of patients, unlike in studies from India, where crustacean allergy was not seen.^5,31,34

Among Chinese children there is a high prevalence of crustacean allergy^22,23 and it is the leading cause of food allergy among younger children in some south East Asian countries such as Vietnam,²⁹ Taiwan,²⁵ and Hong Kong,²⁴ but is less common in Japan²⁸ and South Korea.¹⁹ It is seen in older children and adults in Japan²⁸ and Vietnam³⁰ and is the commonest adult food allergy in Singapore.²⁷ Crustacean allergy is less common in Europe and United States.^16,34, 35, 36 The early introduction of shellfish and consumption of raw food have been considered as causes for this phenomenon.⁴⁰ Shellfish is not consumed raw, and is not a food that is introduced early in Sri Lanka. Another possibility is cross reactivity to house dust mites (HDM) and cockroaches, in tropical climes with high humidity.^40,41 However, data from India, with similar levels of humidity and exposure to HDM, reveal that, while sensitization to shrimp is high, there was no clinical allergy^5,31,34

Peanut allergy was not seen in children born in Sri Lanka. The prevalence of peanut allergy is 1–2% in the west, but uncommon in Asia and other areas,⁴² including India and China.⁵ Two children, born in Europe but residing in Sri Lanka after infancy had peanut allergy. Asian children born in Australia had higher peanut allergy, compared to children from the same ethnic group born in their native country but who had subsequently migrated to Australia.⁴³ Early introduction of peanuts reduces the risk of peanut allergy.⁴⁴ Introduction of peanuts at 6–12 months is recommended in Sri Lanka, which may explain the low incidence of peanut allergy in our study population.⁴⁵

Fish allergy is rare in Sri Lanka similar to India, where clinical allergy was not detected.⁵ Fish allergies are relatively uncommon in South East Asian countries, even though there are regional differences.¹⁶ Philippines has a relatively high rate of fish allergy⁴⁶

Primary wheat allergy is less common in our population compared to Japan,²⁶ Korea,²¹ and United States,⁴⁷ but commoner than in India and other Asian countries.¹⁶ Sensitization to wheat was common in adults in the Indian study, but symptomatic wheat allergy was rare.⁵

Anaphylaxis

A majority of patients in our cohort had anaphylaxis, the probable reason being minor allergies not being referred to our unit for further investigation.

FDEIA was common in our cohort from 5 years of age, and was the commonest cause after 12 years. The reason for the high prevalence is possibly because many clinicians were unaware of the condition and referred such patients to our clinic. Wheat was the only food identified. While wheat is the commonest allergen, other foods are also implicated elsewhere.¹⁰

Red meat was the commonest allergen in the 5–12-year age group, and was the second most common in adults. In addition, patients with red meat allergy developed allergic reactions including anaphylaxis, to vaccines containing bovine/porcine components such as the measles, mumps, and rubella (MMR) and the live Japanese encephalitis (JE) vaccine. Allergy to bovine/porcine excipients have been implicated in allergic reactions to these vaccines.⁴⁸ Patients with CMA⁴⁸ or red meat allergy⁴⁹ may be at risk and therefore caution should be exercised when administering such vaccines. Gelatin or BSA⁴⁹ has been implicated as the culprit allergen. JE is a single dose vaccine, and most MMR reactions occurred with the second dose;⁴⁹ the need for further vaccines did not arise in a majority of these patients. Unfortunately, vaccines free of bovine excipients are not available in Sri Lanka. Patients with alpha-gal allergy were not at risk of vaccine allergy, possibly due to its onset being after the age of immunization with these vaccines.

Cow's milk was the most common cause of anaphylaxis in children below 5 years, as in other countries. Coconut was the second commonest cause of anaphylaxis in infancy. Coconut is part of the daily diet of a majority of Sri Lankans, and is a weaning food. Although data regarding coconut (Cocos nucifera) allergy is limited, a recent Australian paediatric case series reported 35 patients with allergy to coconut including 9 with anaphylaxis. ⁵⁰ Anaphylaxis to hen's egg was uncommon, contrasting with data from Europe,⁵¹ China, Japan, Korea, and Singapore.⁵² Anaphylaxis to nuts and peanuts was uncommon similar to South Asia, but is relatively common in Hong Kong, Singapore, and in Europe and Australia.⁸

Anaphylaxis to fruits was also very rare in our population. This contrasts with the rest of the world, where it is common.⁸ Anaphylaxis due to ingestion of horse purslane (Trianthema portulacastrum), locally known as "Sarana", was identified in 1 patient. This has not been reported previously.

Pollen food allergy syndrome

No patient had pollen food allergy syndrome (PFAS). There are case reports of PFAS from India, ⁵³ but they are rare compared to the west. The reason for this discrepancy is unclear.

The present study was limited to patients referred from other centers for evaluation of food allergy. Some patients in whom the implicated food was easily identified may not have been referred to our unit, even though this may be a small number as our clinic is the only unit in the country offering diagnostic services, free of charge. In addition, we did not offer oral food challenges, which is the gold standard for food allergy diagnosis. However, the patients were included in the present study if they had clear evidence of allergy along with ingestion within 2 hours of onset of symptoms (except in FDEIA and alpha-gal allergy).¹¹

Conclusions

The main cause of food allergy in children was CM, whereas FDEIA and red meat allergy were common causes of food allergy/anaphylaxis in older children and adults. Red meat allergy was also implicated in allergic reactions to some childhood vaccines. Primary red meat allergy may be responsible for late onset CMA.

Abbreviations

CM; Cow's Milk, CMA; Cow's Milk Allergy, CRD; Component Resolved Diagnostics, FA; Food Allergy, FDEIA; Food Dependent Exercise Induced Anaphylaxis, HDM; House Dust Mites, IgE; Immunoglobulin E, LTP; Lipid Transfer Proteins, PFAS; Pollen Food Allergy Syndrome

Declaration of competing interests

The authors declare that they have no competing interests.

Funding source

Self-funded.

Ethics statement

Ethics approval was provided by the Ethics Review Committee, Medical Research Institute, Colombo 08, Sri Lanka (ERC approval No: 01/2022).

The data were analyzed retrospectively and anonymized.

Authors' contributions

RDS, DD– conception, design of the work, acquisition, analysis, interpretation of data, drafted the work and substantively revised it.

CK- acquisition.

JI- acquisition, analysis.

Consent for publication

The authors have given their consent for the publication.

Availability of data statement

All (anonymized) data are available with the corresponding author.