Food Allergens

Food allergy is the term given to hypersensitive response induced in a healthy human individual due to certain food or food additive. And food allergen is naturally occurring proteins in food & food additives that can trigger the immune response causing hypersensitivity. Being a global problem, approximately 25% population in India suffers from a food allergy, which is comparatively low to western countries where the percentage is high up to 40%. The percentage of food allergies in children is higher than that in adults. Allergies can be out-grown with age, might develop in the later phase of life, or may remain lifelong. Earlier due to lack of knowledge regarding consequence and non-specific and a wide range of symptoms of food allergy, medical or concerned authorities did not entertain cases. Hence, the first reported case was in the 20th century and allergy caused was due to dairy products.

As the effect of food allergens can toxic or nontoxic in nature, food manufacturing industries, as well as government regulatory authorities, are putting considerable effort into combating the issues caused by food allergens by promoting awareness and prevention methods and one such initiative is the labeling of allergens on the packs. The non-existence of any specific cure to food allergy, prevention possible by getting self-aware of the food items one is allergic and avoiding the consumption of all foods containing the allergen.

The response of Food Allergen

Hypersensitivity by individual Food allergens can stimulate different types of responses. It can be either toxic or nontoxic in nature. Figure 1 shows the response and its classification and figure 2 summarizes the sub-classification used for food Allergen & food intolerance.

Fig.1 Classification depending Responses of Food Allergen


Fig. 2 Subclassification of Nontoxic type of allergen

Food sensitivity response can be

  1. Immediate Type Food Allergy Response – Most commonly seen in young children that show an allergic reaction when containing allergic food. In adults it’s generally observed, when a specific food item is combined with alcohol, exercise, or non-steroidal drugs chances are quite high to an allergic reaction.
  2. Delayed-onset Type Food Allergy Response– Occurrence of allergic response is after several hours or days. It is an autoimmune disease (Type III food allergy), where immune cells in the body recognize the allergen protein and produce compounds such as histamines and other chemicals.

Is Food intolerance the same as that to Food Allergen?

Two terms are highly confused to be same but it is not. Food intolerance is the body’s abnormal reaction to food, but in a way that does not involves the immune system. On the other hand, a food allergy is triggered by an immune response. When comparing the two, a food allergy poses a much greater health risk than food intolerance.

Mechanism of Allergen

The human immune system tends to produce antibodies against the entry of any pathogenic or foreign compound. These produced antibodies in response to pathogen entry that may be caused due to the entry of pathogens. This is how the human body protects itself through the inbuilt immune system. Food Allergens develop quite similar conditions in the human body in case of an IgE mediated allergic reaction. When food allergens are ingested, our body’s defense system secretes and distributes IgE antibodies (Immunoglobulin E) in the body. Some of the IgE antibodies come in contact with mast cells and form the sensitized cell. Sensitized cells react with allergic proteins, forming chemical substances such as histamines and other compounds that escalate the allergic symptoms in the body known as hypersensitivity.

Food Allergens

All food poses a threat of being food allergen, however, Codex Alimentarius Commission (CAM)   published a list of most common IgE mediated allergy-causing food.

  1. Cow’ milk
  2. Chicken Eggs
  3. Legumes (Peanuts, gram beans, green peas)
  4. Tree Nuts (Almonds, Cashew, Pistachio, Walnut)
  5. Sea Foods (Crustaceans, Fish)
  6. Cereals (Wheat, Barley, Rice, Corn, Sorghum)
  7. Spices (Turmeric, Cumin seeds)

Other Allergens- Apart from the above-stated list, there are few fruits and vegetables (Apple, Peach, Carrot, Tomato, and Banana, etc.)  that has shown the potential of being allergic but has not been included by CAM and causes Oral Allergy Syndrome (OAS)


Allergy causing protein can affect the functioning of the human body leading to disease related to skin, gastrointestinal, digestive, respiratory, and cardiovascular. Most common symptoms are skin rashes, flushed skin, hives, itchy sensation in the mouth, swelling of face, lips & tongue, abnormal cramps, vomiting, nausea, diarrhea, or constipation, wheezing & coughing, difficulty in breathing and loss of consciousness.

Apart from such unspecific & common issues, at times, a food allergy can pose a threat to life. Anaphylaxis is one of the most common conditions that yearly results in deaths. This condition leads to a drop in blood pressure, suffocation, and breathing problems due to swelling in the throat and airways in the lungs.    

Fig. 3 List of Organ & health issue caused   

Food Induced Disorders

Some of the major disorders along with their symptoms on infected individual along with the common causal food ingredient has been listed in the table below:- 



Causal Food

Urticaria/ angioedema

  1. Ingestion or direct skin contact
  2. Acute urticaria
  1. Major allergens

Oral allergy syndrome

  1. Pruritus, mild edema confined to the oral cavity
  2. Anaphylaxis
  1. Raw- fruit/vegetables
  2. Cooked- apple, peach, pear, Carrot, melons

Rhinitis, asthma

  1. food-induced allergic reaction
  1. Major allergens


  1. Cardiovascular collapse
  1. Peanut, tree nuts, shellfish, fish, milk, egg




(Food triggers anaphylaxis only if ingestion followed temporally by exercise)

  1. Wheat, shellfish, celery

Atopic dermatitis

  1. Moderate-to- severe rash
  1. Major allergens
  2. Egg and milk



  1. Inflammation
  2. Esophageal: dysphagia and pain
  3. Ascites, weight loss, edema, obstruction
  1. Major allergens

Dietary protein


  1. Emesis
  2. Diarrhea
  3. poor growth
  4. lethargy
  1. Cow’s Milk, soy, rice, oat

Dietary protein


  1. Mucus-laden
  2. Bloody stools in infants
  1. Milk (through breastfeeding)

 Precautionary Steps  

  1. Avoidance: Avoidance is the rejection of foods that can cause an allergic reaction in any individual is highly recommended. It shall be helpful to be fully aware and note down of any history pf allergic reaction by consuming any specific food item and eliminating it from the diet.
  2. Food Labelling: Manufacturing Industry should let know their consumer if the product contains any type of allergen material or has been processed in a line that has been used for manufacturing allergen-containing products. This type of cautionary label is required, as chances of cross-contamination cannot be denied if the same processing line is being used for allergen and non-allergen products.

Way Forward

Allergen management in the food industry is highly advisable and for more detailed information and understanding of DO’s and DO NOT’s of the food industry, refer the following link.

Having a diverse food culture in India, there are many food items that can lead to food allergy however, the majority of them are not life-threatening. Sometimes mild symptoms during the early phase may escalate with time leading to conditions such as anaphylaxis. Children being prone to these allergies due to weak immune system have chances of outgrowing the allergy with time. No current treatment has led to avoidance as an only preventive method, which has opened up vast opportunities for research & development in this field. It is one of the most challenging clinical problems and has major public importance.


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