What to do in case of a food allergy on the skin?

The very first instinct in the event of a food allergy is to assess the severity of the reaction. In most cases, this is limited to a skin rash of the urticaria type, characterized by raised, itchy red patches. However, it can happen that the swelling of the skin affects the larynx or pharynx, leading to a major respiratory discomfort. This type of food allergy represents an absolute medical emergency, due to the accompanying risk of choking. Another danger found in certain food allergies is anaphylaxis, a severe, potentially fatal allergic reaction. It manifests as breathing difficulties, swelling of the face or throat, nausea, vomiting, a drop in blood pressure, and dizziness.

In the event of an allergic angioedema with anaphylactic shock, it is crucial to immediately call for emergency assistance by dialing 15 for SAMU in France, 911 in the United States, 999 in the United Kingdom, or 116 117 in Germany.

While waiting for help, if the person affected by the food allergy carries with them a dose of injectable adrenaline, often presented in the form of an auto-injector pen, also known as an epipen, it must be urgently administered. If there is no response within five to ten minutes, a new dose can be injected. Adrenaline typically acts within a few minutes to decrease vasodilation, increase blood pressure, and reduce swelling. The patient should then be transported to the hospital, where they will receive additional care.

Some allergic reactions can be quite impressive and affect the entire body.

If a food allergy only affects the skin and does not appear to pose a risk of anaphylactic shock, it is not necessary to alert emergency services. However, it is advised to consult a doctor promptly to ensure this and receive appropriate treatment. Most often, antihistamines are prescribed to reduce allergic symptoms. As their name suggests, these medications work by blocking the specific receptors of histamine, thus preventing the attachment of this mediator and the cascade of inflammatory reactions it triggers.

In cases where antihistamines are ineffective and the allergic skin reaction persists, a doctor may prescribe dermocorticoids, such as hydrocortisone or betamethasone. These creams reduce local inflammation by inhibiting the release of pro-inflammatory cytokines and reducing the activity of the transcription factor NF-κB through the activation of the IkB gene transcription, thereby helping to alleviate inflammatory symptoms. However, corticoids should not be used over an extended period as they can lead to thinning and weakening of the skin.

Once the reaction is managed, it is crucial to ensure that it does not recur in the future by proceeding with the elimination of the responsible food allergen. To do this, it must first be identified, which can be done during an allergy assessment conducted by an allergist. Most often, a prick test is performed. This test involves placing a drop of several allergens on the skin, then lightly pricking it to allow the substances to penetrate the epidermis. In case of an allergy, swelling, redness, or itching appear within a few minutes at the injection point of the allergen.

If the prick test does not yield results, the allergist may perform a specific IgE assay, which involves a blood test. To be considered normal, the total IgE levels in the blood should be less than 150 IU/ml (International Units per milliliter). If this value is exceeded, an allergy is suspected.

The identification of the responsible food allergen must absolutely be done with an allergist and not independently at home, in order to avoid a new allergic reaction, potentially serious.

Once the allergen is identified, it is essential to adapt one's diet to prevent recurrences. This involves completely eliminating the offending food and carefully reading the labels of food products to spot potentially hidden allergenic ingredients. Terms such as "traces of" or "produced in a facility that handles allergens" should not be overlooked and can alert to the allergenic potential of a food.

Informing your loved ones is also a good practice to adopt when suffering from food allergies, especially if they often invite you to lunch or dinner. In addition, it's beneficial for them to know how to recognize the signs of a severe allergic reaction, such as anaphylaxis. Explaining to those around you how to use an adrenaline auto-injector pen can also make a difference in an emergency situation.

Note : Just because your child suffers from a food allergy doesn't mean they can't have lunch at the cafeteria. If you wish to enroll them, you simply need to establish an Individualized Welcome Plan (IWP) with their school.

• WERFEL T. Skin manifestations in food allergy. European Journal of Allergy and Clinical Immunology (2004).

• PUCCI S. & al. Allergy and the skin. Clinical and Experimental Immunology (2008).

• WATSON W. & al. Food allergy. Allergy, Asthma & Clinical Immunology (2011).

• SIMON D. & al. Update on skin allergy. European Journal of Allergy and Clinical Immunology (2014).