Strange to say, some people are not allergic when they are children, but allergic when they grow up; There are also people who are allergic when they are young, and when they grow up, their symptoms become milder and milder, or even no longer have attacks.
Between age and allergies, there seems to be some hidden "secrets". Why is that?
The "secret" between allergies and age
First, the causes of allergic diseases are complex and are often the result of genetic and environmental interactions. When we are young and grow up, the living environment and body conditions are different, and the symptoms of allergic diseases may change to a certain extent.
Secondly, the appearance of allergic disease symptoms depends on repeated stimulation and contact of allergens, and if the allergen is effectively avoided or the exposure of allergens is reduced, allergic symptoms may be reduced or even disappeared. For example, patients with an allergy to animal dander do not develop allergy symptoms until they have a cat or dog at home for a period of time; If you don't have a pet when you are young, you will naturally have a situation where you are not allergic to pets when you are a child, and you will be allergic to pets when you grow up.
Third, the child's immune system is not fully developed and the gastrointestinal barrier function is poor. Therefore, as we age, some children may experience improvement or even tolerance of food allergy symptoms. For example, more than 50% of children who are allergic to milk and eggs can develop spontaneous tolerance after 5~10 years old and last for life. However, most foods cannot be tolerated spontaneously, such as peanuts and tree nuts, and the probability of spontaneous tolerance in patients is low.
In general, patients who "did not have allergies when they were children, but became allergic when they grew up", although they carried allergy susceptibility genes (not single genes but polygenes), but were not exposed to the allergen environment when they were young or the exposure time was not enough to induce an immune response, so no allergy occurred. However, the genetic factors of allergies (i.e., susceptibility genes) will always accompany him to grow up, and when he is continuously exposed to one or more allergens for a long time, his immune system overresponds, resulting in sensitization, which gradually progresses to allergies.
Patients who "have allergies when they are young, but the symptoms become milder and milder when they grow up, and even eventually heal" are often allergic to a few foods. These allergenic foods are generally milk, eggs, etc. The intensity of most allergens such as milk and eggs gradually decreases with age, and more than two-thirds of children will tolerate milk and eggs after the age of 12.
In addition, some patients are allergic to certain inhaled allergens in the air, such as Artemisia pollen, as children. When the patient grew up and settled in the south, there were no artemisia plants in the local environment, no artemisia pollen drifted in the air, and the patient naturally "healed". However, some inhalation allergens such as dust mites are distributed all over the world, and patients have nowhere to hide, and dust mites will be encountered everywhere, and lifelong allergies may occur.
Allergies "progress" with age
Different age groups with high incidence of allergic diseases are different, and the same patient may also have different kinds of allergic diseases at different ages.
Previous studies have shown that the onset of allergic diseases follows a chronological sequence, such as the higher incidence of infantile eczema, atopic dermatitis, and food allergy in infancy, and may progresse to allergic rhinitis and allergic asthma in childhood. This suggests that allergic diseases evolve from the skin to the gastrointestinal tract to the respiratory tract, a phenomenon also known as "The Atopic March." Of these allergic diseases, some gradually disappear as the patient ages, while others persist for many years.
Eczema and atopic dermatitis in infants are the first diseases that appear in the allergic process. It is a chronic recurrent skin disease characterized by chronic inflammation of the skin, itching, and impaired skin barrier. Atopic dermatitis tends to appear early in life. Forty-five per cent of children with atopic dermatitis develop within 6 months of age, and its prevalence increases with age. It was previously thought that more than 50% of children with eczema and atopic dermatitis would be cured within the age of 10. However, the current study shows that atopic dermatitis can be divided into four different types: infants, children, adolescents/adults, and senile types, of which the senile type, that is, patients with atopic dermatitis over 60 years of age, may have more severe itching symptoms. Some scholars believe that aging itself may be a risk factor for the onset or worsening of the disease. Such patients are also gradually receiving more attention. Infantile eczema and atopic dermatitis are partly related to allergies, and most or even the vast majority of adult atopic dermatitis has little to do with allergies.
IgE-mediated food allergy, which usually coexists with atopic dermatitis in early childhood, is one of the earliest manifestations of the allergic process. As mentioned earlier, some food allergies may gradually improve with age and develop tolerance.
The disease in which the allergic process eventually progresses is allergic rhinitis or allergic asthma. Studies have shown that infants and young children with atopic dermatitis under the age of 2 have a significant increase in the incidence of allergic rhinitis and asthma at the age of 6~7. Among them, children with early age of onset, repeated prolongation, and positive for certain food-specific IgE are at higher risk of subsequent allergic diseases. Also because of "the same airway, the same disease", the incidence of asthma in children with allergic rhinitis is also significantly increased. If these children do not receive standard treatment, the symptoms of allergic rhinitis and asthma may persist with age and worsen year by year. Studies have shown that increasing age is also an independent risk factor for poor asthma treatment.
The earlier you intervene, the better
A small number of food allergies can be spontaneously tolerated by the body with age, which is manifested by the patient's symptoms becoming milder, such as milk and egg allergy in childhood, active symptomatic treatment and avoiding diet, and the patient will gradually improve as he grows up. Nuts, seafood, etc. have long-term persistent food allergic reactions, and the treatment of patients is mainly based on reasonable avoidance of diet, even in adulthood, they should be vigilant against allergies caused by accidental ingestion. If the patient has developed anaphylactic shock from eating a certain food, such as nuts, it is important to strictly refrain from eating (including any food that may contain nuts or even very small amounts of nuts) and actively follow specialist advice.
Patients with allergic rhinitis, allergic asthma, and atopic dermatitis who can identify the allergen causing the symptoms should first avoid the allergen. If the patient cannot avoid contact with the allergen and symptoms recur, allergen-specific therapy, that is, desensitization therapy, should be started as soon as possible. Desensitization therapy is the only causative treatment for some type I allergic diseases (specific IgE-mediated), which can induce the body to gradually develop immune tolerance, thereby reducing symptoms, reducing the use of symptomatic treatment drugs, and receiving immunotherapy as soon as possible can delay the allergic process and prevent the occurrence of new allergies. Especially in children, the immune response to allergens is different from that of adults, and the plasticity is strong. Early desensitization therapy in children with allergic asthma is more likely to block the progression from allergic rhinitis to asthma and from monosensitivity to multiple sensitization, thereby altering the natural course and long-term outcome of asthma.
Source: Public Health magazine
Author: Beijing Shijitan Hospital, Capital Medical University
Allergology Chen Lijia Wang Xiaoyan
Review: Expert of the National Health Science Popularization Expert Database
Professor of Allergology at Peking Union Medical College Hospital Wang Lianglu
Curator: Wu Weihong
Editor: Luan Zhaolin