A review study analyzed the current knowledge on food allergies in children and the potential of food immunotherapy as a mainstream treatment.
Food allergies have always been a health concern due to their potential to cause life-threatening reactions, even when a tiny amount of food is consumed. Research has shown a 50% increase in food allergies in the USA between 1997 and 2011, and nearly 8% of American children are now food allergic.
Allergies are triggered by allergens, which are antigens found mainly in proteins. These antigens may also be present in some carbohydrates and lipids that are able to induce abnormal immune responses.
The most common food allergens are milk, egg, soy, wheat, peanut, nuts, fish, and shellfish. For children, most allergic reactions are caused by cow’s milk, hen’s eggs, and peanuts. Peanuts are the most common cause of an extreme allergic reaction called food-induced anaphylaxis.
Some studies suggest that milk, egg, soy, and wheat allergies can be overcome, while others cannot. The causes of food allergies are not yet known but researchers believe it is due to a loss of oral tolerance or a delay in the oral tolerance development during early childhood. They suggest that introducing allergens earlier in childhood could prevent the development of allergies later.
Currently, the only effective treatment for food allergies is the strict avoidance of the allergen and immediate treatment of the reactions. Allergen immunotherapy has shown promising results in the treatment of pollen and insect venom allergic reactions, and now researchers are assessing the efficacy and safety of food allergen immunotherapy for children.
The purpose of food immunotherapy is to increase an individual’s threshold of sensitivity to the food they are allergic to. This is done by administering increasing doses of the allergen daily. The process is called desensitization. Once desensitization is achieved, the next step is to develop sustained unresponsiveness. This is the ability to tolerate the dose without experiencing an allergic reaction after a prolonged period of discontinuing treatment.
According to an article published in April 2018 in the pediatric journal Children, studies on food allergies have reported that sustained unresponsiveness varies according to the route of immunotherapy, which can be oral, sublingual, or epicutaneous.
Currently, there is no treatment regimen establishing the ideal doses and intervals for food immunotherapy, and protocols vary widely between food allergies studies. Patients who undergo this kind of therapy often face mild to moderate side effects.
Some factors may also increase the risk of side effects, such as viral infections, menses, and even exercise. Also, patients with a history of poor compliance with medication, asthma, eczema, eosinophilic gastrointestinal diseases, and allergic rhinitis are not eligible for food immunotherapy.
At the beginning of oral immunotherapy, a very small dose of the food allergen (1-25 mg) is administered daily for two to three weeks. The doses increase progressively until a maintenance dose is achieved (300 mg up to 4,000 mg), which might occur after six to twelve months of the regimen.
Following this protocol, about 70% of patients with food allergies achieve desensitization. However, mild to moderate adverse reactions are common, with oral itching and chronic gastrointestinal symptoms being the most frequent. Some patients may also report anaphylaxis. The risk of such reactions increases if doses are taken irregularly.
So far, oral immunotherapy has been used to treat milk, egg, and peanut allergies in children, and a study showed that 50% of school age and older children, and 75% of infants and toddlers achieved sustained unresponsiveness.
In sublingual immunotherapy, the food allergen is administered in a liquid form, held under the tongue for a few minutes and swallowed. The typical starting dose is much lower than the ones used in oral immunotherapy, sometimes even in micrograms, and escalates up to a maintenance dose of no more than 10 mg, which makes this method less effective than oral immunotherapy. However, the side effects caused by sublingual immunotherapy are milder, less frequent, and restricted to the oropharynx, while systemic reactions are rare.
So far, clinical trials conducted for milk, peanut, hazelnut, peach, and kiwi allergens have shown little to none sustained unresponsiveness after treatment discontinuation, which suggests that sublingual immunotherapy might not be an effective option to address food allergies.
In epicutaneous immunotherapy, an adhesive patch is applied to the back or inner arm and worn for 24 hours. Fixed daily doses (250 ìg) are recommended in order to achieve and maintain food protein desensitization. Studies have shown that 90% of study subjects had mild local reactions, while a clinical study reports a response rate difference of 34.2% after 12 months of 250 μg peanut epicutaneous immunotherapy versus placebo in 6 – 11-year-olds with food allergies.
The application of oral, sublingual and epicutaneous immunotherapy is a promising approach for treating food allergies in children. This is because there is still no cure for food allergies and the only treatment currently available is by strictly avoiding food allergens and managing allergic reactions.
Healthcare professionals should be informed about these options and be able to identify patients who could benefit from these forms of food immunotherapy, as they would significantly improve the quality of life for patients and their families.
Written by Gustavo Caetano, B.Sc., M.Sc.
Reference: Anvari S, Anagnostou K. The Nuts and Bolts of Food Immunotherapy: The Future of Food Allergy. Children. 2018, 5, 47.