Atopic diseases are a group of medical conditions characterized by an overreactivity of the immune system to normally harmless substances, such as pollen, dust, animal hair, or certain foods. These pathologies, grouped under the term "atopy", mainly include atopic eczema , allergic rhinitis, allergic conjunctivitis and allergic asthma. They often occur in childhood, but can persist into adulthood. The common factor in these diseases is an exaggerated immune response , which causes various symptoms affecting the skin, respiratory tract, and mucous membranes.
1. The basics of atopy: genetic predisposition and environmental factors
Genetic predisposition plays a crucial role in the development of atopic diseases. If a parent is atopic (i.e. suffers from one or more atopic diseases), the chances of the child developing atopy increase considerably. However, this genetic susceptibility alone is not enough to explain the onset of symptoms. Environmental factors add to this predisposed background to promote the onset of these diseases.
Environmental factors include exposure to allergens such as animal hair , dust mites, mold, pollen, but also air pollution and passive smoking. The modern lifestyle, with processed food, increased hygiene and decreased contact with nature, is often pointed out as an indirect cause of the increase in atopic diseases. The hygiene hypothesis, for example, suggests that reduced exposure to infectious agents during early childhood impairs the normal development of the immune system, thus promoting inappropriate immune reactions .
2. Atopic eczema: an inflammatory skin disease
Atopic eczema , also called atopic dermatitis, is one of the main atopic diseases. It is a chronic inflammatory skin disease that causes dry skin, intense itching and the appearance of red patches sometimes accompanied by small oozing vesicles. This disease often begins in the first months of life and affects approximately 15 to 20% of children in industrialized countries.
Atopic skin is characterized by a defective skin barrier, making it more permeable to allergens and irritants. This leads to persistent inflammation, which is accompanied by itching and rashes. The majority of atopic dermatitis occurs in children, and although eczema often improves with age, some individuals will continue to suffer from it into adulthood .
Environmental factors can make atopic eczema worse, including weather changes (dry, cold or excessive heat), irritants such as soaps or detergents, and allergens in the environment (pollen, animal hair). Certain foods can also trigger flare-ups in people with atopic dermatitis, although this is more common in young children.
3. Allergic rhinitis: an inflammation of the upper respiratory tract
Allergic rhinitis is another common atopic disease, characterized by inflammation of the upper respiratory tract, especially the nose. It occurs in response to allergens such as pollen (hay fever), dust mites, animal dander, or mold. Symptoms include sneezing, runny or blocked nose, itchy nose, and sometimes loss of smell.
Allergic rhinitis is more common during certain times of the year, especially in spring and autumn, when there is a high concentration of pollen in the air. However, it can also be permanent in people who are continuously exposed to household allergens such as dust mites or pets.
People with allergic rhinitis are often susceptible to other atopic diseases, including allergic asthma and allergic conjunctivitis. The link between rhinitis and asthma is well established, as untreated nasal inflammation can worsen lower airway inflammation, triggering asthma attacks in susceptible individuals.
4. Allergic conjunctivitis: an inflammation of the eyes
Allergic conjunctivitis is an inflammation of the conjunctiva, the membrane that covers the white of the eye and the inside of the eyelids. It is caused by an allergic reaction to substances such as pollen, animal hair, or dust. Symptoms include red, itchy, burning, or watery eyes, and a foreign body sensation in the eye.
Although benign, allergic conjunctivitis can be very uncomfortable and often interferes with daily activities. As with other atopic diseases, it is linked to an overreaction of the immune system . It is frequently associated with allergic rhinitis, and people with one disease often develop the other.
5. Food allergies: a risk for atopic children
Food allergies are common in people with atopic dermatitis, especially in young children. In fact, it is common for a child with atopic eczema to develop an allergy to a food, often in the first few years of life. The most common food allergens are cow's milk, eggs, peanuts, tree nuts, fish, and shellfish.
Immune responses caused by food allergies can cause a variety of reactions, ranging from skin symptoms (hives, eczema) to gastrointestinal symptoms (vomiting, diarrhea) and even serious reactions such as anaphylaxis, which requires emergency medical intervention.
Children with atopic dermatitis are at increased risk of developing food allergy, partly because of the impaired skin barrier. This allows food proteins to come into contact with the immune system through the skin, leading to sensitization.
6. The evolution of atopic diseases over time
Atopic diseases often progress over the years, in a phenomenon known as the "atopic march." This term refers to the typical progression of atopic diseases, which usually begins with atopic dermatitis in infants, followed by the development of allergic rhinitis and allergic asthma as the child grows.
Although some children with atopic eczema never develop other atopic diseases, many will develop a respiratory allergy such as rhinitis or asthma during their lives. It is also possible for atopic symptoms to improve over time, but some people will continue to suffer from these diseases into adulthood , although the intensity of symptoms may decrease.
Regular medical monitoring and adequate symptom management are essential to avoid complications and improve the quality of life of atopic patients. Treatment is mainly based on allergen avoidance, the use of anti-inflammatory drugs such as corticosteroids, antihistamines to relieve symptoms, and in some cases, desensitization (immunotherapy).
7. Treatment and management of atopic diseases
Cases of atopic dermatitis require appropriate medical care, particularly when the disease is severe or resistant to usual treatments.
The first line of treatment includes regular application of emollients to maintain skin hydration and repair the skin barrier. In cases of inflammatory flare-ups, topical corticosteroids or calcineurin inhibitors are often prescribed to reduce inflammation and calm itching.
In some cases of severe atopic eczema , systemic treatments such as immunosuppressants or biotherapies may be considered to control chronic inflammation. These treatments are generally reserved for the most severe forms of the disease, when topical treatments are no longer sufficient to manage symptoms.
For allergic rhinitis and allergic conjunctivitis , treatment is primarily based on antihistamines, which reduce the allergic reaction and associated symptoms. In some cases, the use of nasal corticosteroids may be necessary to control upper airway inflammation. Allergen desensitization, or immunotherapy, may also be considered in patients with severe or persistent rhinitis. This treatment involves gradually exposing the patient to increasing doses of the offending allergen in order to reduce the sensitivity of the immune system.
For food allergies , the main strategy remains strict avoidance of the offending food, with increased vigilance to avoid cross-contamination. For patients at risk of anaphylaxis, the prescription of an emergency kit including adrenaline is essential.
Conclusion
Atopic diseases are a group of chronic inflammatory pathologies that result from an exaggerated immune reaction to common substances in our environment. Atopic eczema is a common disease in children, but other diseases such as allergic rhinitis, allergic conjunctivitis and food allergies can also occur in atopic people.
Genetic predisposition , combined with environmental factors , plays a key role in the development of these diseases. Although symptoms can change over time, requiring management adapted to each stage of life, it is possible to effectively manage these pathologies through specific treatments and a healthy lifestyle.
In conclusion, although atopic diseases can persist into adulthood, early and appropriate management often limits their impact on patients' quality of life and avoids long-term complications.