Food allergies, how to recognize them?
What are the signs?
What tests should be done?
What are the symptoms of a food allergy
The onset of symptoms is usually very fast, a few minutes to 4 hours after ingestion of the food. But in cases of eczema and gastrointestinal symptoms, the symptoms are permanent or appear in delays of up to several days after consumption of the food.
Symptoms after the consumption often appear sometimes smell (steam inhalation of food), or by skin contact with the food or cosmetics containing food proteins.
Recognize the symptoms of a food allergy can be tricky, because they are different and all parts of the body can be affected (Table 2). Signs and are often associated with cutaneous signs are more common in children.
Table 2. Signs of food allergy.
Skin symptoms (skin) and mucosal
- Acute urticaria greater or lesser extent
- Eczema
- Angioedema (swelling of eyelids, lips, tongue, larynx in the most severe forms)
Gastrointestinal symptoms
- Oral Allergy Syndrome (has a tingling in the mouth and throat, swelling of the lips and feeling when swallowing gene).
- Nausea
- Vomiting
- Abdominal pain
- Diarrhea, bloody stools
- Growth retardation, sleep disorders, irritability in infants
Respiratory symptoms
- Rhinitis, rhinoconjunctivitis
- Laryngeal edema
- Cough, wheezing, difficulty breathing
- Asthma
Anaphylactic shock
It is the majority solemn manifestation of food allergy that requires instant treatment. It frequently begins with malaise, followed by itchy hives or complexity breathing. From time to time loss of consciousness related with a voltage drop is pragmatic. This is a true medical emergency requiring immediate care (call SAMU)
What tests should be done?
Identify a food allergy begins with a careful designed to clarify the family and personal history, what foods were consumed, the time to onset of symptoms after ingestion of food or suspects.
The diagnostic approach to food allergy occurs in 4 steps.
Step 1: The dietary survey carried out 7 days to define the chronological relationships between food intake and suspicious symptoms.
Step 2: Skin tests / patch.
Skin tests (skin) are made by the prick test technique that involves placing a drop of allergen on the skin and then make a stitch through the drop of reagent. Tests are carried on the arm or on the back, and reading is done after 15 minutes, the time required for the formation of the wheal. Sometimes these tests are performed with a natural food, and include first bite of food and skin. It is necessary to stop before the anti-histamines (at least 3 days).
Patch tests or "atopy patch test" foods are used in individuals who have eczema or gastrointestinal symptoms. Natural foods are placed in wells that are applied at the upper back and maintained by a plaster. Reading test is performed during the withdrawal of the cup at 48 and 72 h after application.
These tests are compared with the clinical history and may be supplemented by further explorations.
Step 3: The biological exploration is performed from blood samples for measuring specific IgE and skin tests complete. Other assays are performed in special cases.
Step 4: Test of oral provocation is the only test to prove the reality of a food allergy. It is supposed to be eating the food allergic conditions of maximum safety, ie in highly specialized hospitals. It identifies the amount of food that causes the symptoms and it defines the type of reaction triggered by the ingestion of food. The test is often preceded by a test application of the food on the lip (labial provocation test).
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