Food allergies are dangerous, as in some cases they may cause death after anaphylactic reactions.

The symptoms related to the severity of the allergic reaction are:

• Sensation of suffocation, hoarseness, throat tightness, difficulty swallowing.
• Wheezes or whistles on inhaling, difficulty breathing, sensation of chest tightness.
• Itching, sensation of generalised tingling in the hands, feet, neck and throat.

These symptoms may occur immediately and they may evolve rapidly from minutes after the ingestion up to one hour afterwards, constituting a medical emergency and requiring immediate treatment with adrenaline.

The most frequent allergies are those that occur as an infant when solid foods are added to the diet after breastfeeding.

Allergy to cow's milk and eggs can frequently occur before one year of age.

Between the age of 1 and 2, allergies to soy, cereals and fish may manifest.

Over the age of 2, allergies to fruit, legumes, cereals and nuts are most frequent, among others.

It is important to keep in mind that food intolerance to lactose may revert with time as enzymes are developed for intestinal absorption, thereby improving intolerance to cow's milk protein which causes chronic diarrhoea, vomiting, atopic dermatitis, etc.

In general, food allergies are for life; in some cases, such as allergy to eggs and cow's milk, they may disappear between the ages of 2 and 4 years of age.

The proteins in cow's milk:
Casein, rennet casein, caseinates, albumin lactalbumin, lactulose. This allergy tends of appear during the first year of life.

Egg protein:
Ovoalbumin, used frequently in the food industry and confectionery industry as an additive, preservative, stabilising agent, artificial colours, artificial flavour, in bread-baking, pasta, ice cream, meringue, marzipan, chocolates, nougats, etc.
It tends to be part of excipients or diluents in preparations such as medicinal products.
Vaccines may also be prepared (measles, mumps, rubella), cultivating viruses in chicken embryo cultures.
Egg allergy is often associated to allergy to cow's milk protein.

Nuts:
Peanuts, walnuts, almonds, oils or derivatives such as peanut flours or butters. Peanut derivatives, such as nuts, oils, flours, butters and condiments, are common in African, Indian, Chinese, Indonesian, Thai, Vietnamese, North American and Mexican food.

Fish proteins:
These allergies are frequent in children and adults. Allergy to white fish (hake, sole, gilthead sea bream, sea bass, trout, etc.) is more frequent than blue fish (red bream, salmon, sardines, anchovies, etc.). Allergies may be caused by inhaling the steam that comes from cooking or frying fish.

Both crustacean shellfish (lobster, prawns, crawfish and barnacles) and molluscs (mussels, clams, oysters, squid, cuttlefish, octopus and snails) may cause severe allergic reactions. Allergies may also be caused by inhaling the products emitted from cooking these foods.

Soy allergy is relatively frequent.

Cereals such as wheat, oats, barley and rye. The allergy occurs because of a common compound called gluten and this allergic disease is called celiac disease.

Fruit such as peaches and the Rosaceae family (apricots, nectarines, cherries, plums, strawberries, pears, apples). Kiwi, banana and pineapple may also be responsible for allergies.

Legumes such as lentils or chickpeas may cause allergies. Allergies to fruit, nuts and legumes often occur together.

Additives such as sulphites, nitrites, glutamates, etc., that serve as preservatives, sweeteners, flavouring agents, artificial colours, emulsifying agents and stabilising agents are listed on food labels under the letter "E", and may be responsible for food allergies or cause the release of inflammatory substances thereby leading to abdominal cramps, skin rashes and bronchial obstruction of non-allergic origin, but undistinguishable from allergic reactions.