Food Allergy: An Overview
FOOD ALLERGY: AN OVERVIEW
MEENAKSHI BHARKATIYA*, KAMAL SINGH RATHORE, ANKUR MAHESHWARI, SUNITA PANCHAWAT, R.K.NEMA
B.N.GIRLS' COLLEGE OF PHARMACY, UDAIPUR-RAJ. 31002
INTRODUCTION
Food allergy is recognized as a common worldwide problem, and, like other atopic disorders, its incidence seems to increase. In the past years, investigations of allergic food proteins and related immunological responses have moved to the molecular level, and the newly-found knowledge might provide novel experimental strategies for the laboratory diagnosis and the immuno-modulatory control of food-induced allergic reactions (1, 2).
Approximately 20% of the population alters their diet for a perceived adverse reaction to food, but the application of double-blind placebo-controlled oral food challenge, the "gold standard" for diagnosis of food allergy, shows that questionnaire-based studies overestimate the prevalence of food allergies. The clinical disorders determined by adverse reactions to food can be classified on the basis of immunologic or no immunologic mechanisms and the organ system or systems affected (3, 4, 5).
The true prevalence of food allergy is lower and seems to range from 1% to 4% of the general population and about 6% of the general population and about 6% of the paediatric population, but does occur in as much as 25% of children with eczema6. Allergic hypersensitivity simply put, is an adverse immune reaction to a protein (or allergen) in our environment, which is normally harmless to the non-allergic person. It may present as mild itching of the skin, tissue swelling and wheezing or even progress to full-blown anaphylaxis and death. 18 million allergy sufferers live in the UK where 4% of the populations also have a food allergy.
Allergy develops after repeated exposure to the causative allergen. Sensitization takes place on initial exposure (a process that may take up to six weeks to develop) and no adverse reaction appears to occur during initial sensitization (6).
(A) DEFINITION
A food allergy is an immunologic response to a food protein and caused by allergens in the food that are a kind of protein in the food. These proteins resist the cooking process, the acid in the stomach and the enzymes in the stomach and intestines and enter the blood stream and they cause the allergy reaction after they enter the blood stream.
(B) SIGNS AND SYMPTOMS
Symptoms of food allergies are: -
1. Anaphylaxis: - a severe, whole-body allergic reaction that can result in death. Leads to vasodilation and, if severe, symptoms of life-threatening shock.
2. Angioedema: - rapid swelling (edema) of the skin, mucosa and submucosal tissues, especially of the eyelids, face, lips, and tongue.
3. Eczema is a form of dermatitis, or inflammation of the upper layers of the skin.
(a). Atopic eczema (aka infantile e., flexural e., atopic dermatitis) is believed to have a hereditary component, and often runs in families whose members also have hay fever and asthma. Itchy rash is particularly noticeable on face and scalp, neck, inside of elbows, behind knees, and buttocks.
(b). Contact dermatitis is of two types: allergic (resulting from a delayed reaction to some allergen, such as poison ivy or nickel), and irritant (resulting from direct reaction to a solvent, for example). Some substances act both as allergen and irritant (e.g. wet cement). Other substances cause a problem after sunlight exposure, bringing on phototoxic dermatitis.
(c). Xerotic eczema (aka asteatotic e., e. craquele or craquelatum, winter itch, pruritus hiemalis) is dry skin that becomes so serious it turns into eczema. It worsens in dry winter weather, and limbs and trunk are most often affected. The itchy, tender skin resembles a dry, cracked, river bed. This disorder is very common among the older population.
(d). Seborrhoeic dermatitis (aka cradle cap in infants, dandruff) causes dry or greasy scaling of the scalp and eyebrows. Scaly pimples and red patches sometimes appear in various adjacent places. In newborns it causes a thick, yellow crusty scalp rash called cradle cap which seems related to lack of biotin, and is often curable.
4. Skin rashes, such as nettle rash (also called urticaria or hives). Some of these longer lasting rashes are called atopic dermatitis.
5. Itching of the mouth, throat, eyes, skin, or any area
6. Nausea, vomiting, diarrhoea, stomach cramps, or abdominal pain
7. Running nose or nasal congestion
8. Wheezing, scratchy throat, shortness of breath, or difficulty swallowing
9. Mood swings, depression: The symptoms of an Immunoglobulin E (IgE) allergic reaction can take place within a few minutes to an hour. The process of eating and digesting food affects the timing and location of a reaction. IgG reactions build over a period of hours to days, and therefore symptoms can be difficult to notice as allergy-related (7).
TYPES OF ALLERGENIC FOOD
There are a number of groups of foods that are responsible for causing the majority of food allergies (6). Rice allergy is more common in East Asia where rice forms a large part of the diet. In Central Europe, celery allergy is more common. The top allergens vary somewhat from country to country but milk, eggs, peanuts, tree nuts, fish, shellfish, soy, wheat and sesame tend to be in the top ten in many countries (8).
The most common food allergies are: -
1. Milk allergy:-
Two out of a hundred infants under one year old suffer from cow's milk allergy, making it the most common food allergy of childhood. In general children lose this sensitivity as they grow up with nine out of ten losing it by the age of three; it is unusual for adults to suffer from this allergy. Symptoms are frequently vomiting and diarrhoea in children, with 30-50% also having skin rashes of some type. A small number of children have an anaphylactic reaction to milk which tends to be life-long.
The major allergens in milk are the caseins and the protein b-lactoglobulin. People are usually allergic to more than one kind of milk protein. The proteins from cow's milk are very similar to those from goats and sheep. Thus goat's or sheep's milk cannot be used as a cow's milk substitute in allergic individuals (8).
A report about 22-year-old Female patient is described who was repeatedly hospitalised on account of severe asthmatic attacks presumably due to the ingestion of cow's milk or milk-containing products. There were no signs of gastrointestinal disturbance, but some urticaria and angioedema occurred. Strongly positive RASTs (radioallergosorbent test) were observed in the blood serum against the proteins in cow's milk, bovine serum, egg white, cod fish, and house dust. The symptoms were successfully controlled by rigorous dietary measures (8).
2. Eggs:-
Allergy to eggs is usually observed in young children rather than adults, and like cow's milk allergy, fades with time. Occasionally children suffer from a severe form of allergy which is not outgrown.
The main allergens are the egg white proteins ovomucoid, ovalbumin, and ovotransferrin. The eggs of other poultry, such as ducks, are very similar to those of hens and can cause reactions in egg-allergic individuals (8).
3. Peanut allergy:-
Peanuts are one of most allergenic foods and frequently cause very severe reactions, including anaphylaxis. Allergy to peanuts is established in childhood and usually maintained throughout life. Peanut allergy can be so severe that only very tiny amounts of peanut can cause a reaction. Thus the traces of nuts found in processed oils, or the carryover of materials on utensils used for serving foods, can be enough in some individuals, to cause a reaction. The main allergens in peanuts and Soya are the proteins used by the seed as a food store for it to grow into a seedling. One of the allergens in Soya bean is very similar to a major allergen from dust mites, a common environmental allergen. We aren't sure yet whether this means there is a link between dust allergy and Soya allergy.
A large number of children who develop peanut allergy have their first reaction the first time they are given a peanut-containing product (usually a dab of peanut butter). A large number of children who develop peanut allergy have their first reaction the first time they are given a peanut-containing product (usually a dab of peanut butter). Peanut protein could pass into breast milk Twenty-three lactating women; aged 21 to 35 years ate 50 grams of dry roasted peanuts (about 60 peanuts or 1/3 cup). Breast milk samples were collected at hourly intervals. Peanut protein was found in the breast milk of 11 of the mothers. In 10 mothers, it was detected within two hours after she ate peanuts, in one mother it was detected six hours later.
That peanut protein is secreted into breast milk, thus sensitizing the baby who is at risk for developing an allergy. This may explain why up to 85 percent of children have a peanut allergy reaction the first time they eat a peanut-containing product. A baby born into a family with allergies.
[Note: - Milk, eggs, and wheat have previously been shown to pass into breast milk. The mothers from allergic families eliminate peanuts and tree nuts (e.g., almonds, walnuts, etc.) and consider eliminating eggs, milk, fish, and perhaps other foods from their diets while nursing. If you choose to do this, be sure to speak with a registered dietitian to be sure your diet is well-balanced (8).
4. Tree Nut