What are atopic diseases?
Atopic diseases represent a group of medical conditions characterized by a hyper-reactivity of the immune system to normally harmless substances, such as pollen, dust, animal hair or certain foods. These pathologies, grouped together under the term "atopy", mainly includeatopic eczema, allergic rhinitis, allergic conjunctivitis and allergic asthma. They often begin in childhood, but can persist into adulthood. The common factor in these diseases is an exaggerated immune response, leading to a variety of symptoms affecting the skin, respiratory tract and mucous membranes.
1. The foundations 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 child's chances of developing atopy increase considerably. However, genetic susceptibility alone does not explain the onset of symptoms. Environmental factors add to this predisposed terrain to favor the onset of these diseases.
Environmental factors include exposure to allergens such as animal hair, dust mites, molds and pollen, as well as air pollution and passive smoking. The modern lifestyle, with its processed food, increased hygiene and reduced contact with nature, is often pointed to as an indirect cause of the increase in atopic diseases. The hygienist hypothesis, for example, suggests that reduced exposure to infectious agents in early childhood alters the normal development of the immune system, thus promoting inappropriate immune responses.
2. Atopic eczema: an inflammatory skin disease
Atopic eczema, also known as atopic dermatitis, is one of the main atopic diseases. It's a chronic inflammatory skin disease that causes skin dryness, intense itching and the appearance of red patches sometimes accompanied by small, oozing blisters. The disease often begins in the first few months of life, and affects around 15-20% of children in industrialized countries.
Atopic skin is characterized by a defective cutaneous barrier, making it more permeable to allergens and irritants. This leads to persistent inflammation, compounded by itching and rashes. The majority of atopic dermatitis appears in children, and although eczema often improves with age, some individuals will continue to suffer from it intoadulthood.
Environmental factors can aggravate atopic eczema, including climatic variations (dry air, cold or excessive heat), irritating products such as soaps or detergents, and allergens present 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: inflammation of the upper respiratory tract
Allergic rhinitis is another common atopic disease, characterized by inflammation of the upper respiratory tract, particularly the nose. It occurs in response to allergens such as pollen (hay fever), dust mites, animal hair or mold. Symptoms include sneezing, runny or stuffy nose, itchy nose, and sometimes loss of sense of smell.
Allergic rhinitis is more common at certain times of the year, particularly in spring and autumn, when there is a high concentration of pollens in the air. However, it can also be permanent in people with ongoing exposure 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 inflammation of the lower airways, triggering asthma attacks in susceptible individuals.
4. Allergic conjunctivitis: 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 sensation of a foreign body 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 excessive immune response. It is frequently associated with allergic rhinitis, and people suffering from one of these diseases often develop the other.
5. Food allergies: a risk for atopic children
Food allergies are common among people with atopic dermatitis, especially young children. Indeed, it's common for a child with atopic eczema to develop a food allergy, often within the first few years of life. The most common food allergens are cow's milk, eggs, peanuts, nuts, fish and seafood.
The immune responses triggered by food allergies can lead to a variety of reactions, ranging from skin symptoms (hives, eczema) to gastrointestinal disorders (vomiting, diarrhea), and even serious reactions such as anaphylaxis, which requires emergency medical intervention.
Children suffering from atopic dermatitis are at increased risk of developing a food allergy, partly due to an 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 evolve 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 onset 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 lifetime. It's also possible for atopic symptoms to diminish over time, but some people will continue to suffer from these diseases intoadulthood, even though the intensity of symptoms may diminish.
Regular medical monitoring and appropriate symptom management are essential to avoid complications and improve the quality of life of atopic patients. Treatment is based mainly on avoiding allergens, using anti-inflammatory drugs such as corticosteroids and antihistamines to relieve symptoms, and in some cases, desensitization (immunotherapy).
7. Treatment and management of atopic diseases
Cases of atopic dermatitis require appropriate medical management, especially when the disease is severe or resistant to the usual treatments.
The first line of treatment includes regular application of emollients to maintainskin hydration and repair the cutaneous barrier. In the event of inflammatory flare-ups, topical corticosteroids or calcineurin inhibitors are often prescribed to reduce inflammation and soothe itching.
In some cases of severeatopic 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 mainly based on antihistamines, which reduce the allergic reaction and associated symptoms. In some cases, nasal corticosteroids may be necessary to control inflammation of the upper respiratory tract. Allergenic desensitization, or immunotherapy, may also be considered for patients suffering from severe or persistent rhinitis. This treatment involves gradually exposing the patient to increasing doses of the allergen responsible, in order to reduce the sensitivity of the immune system.
For food allergies, the main strategy remains strict avoidance of the responsible 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 resulting from an exaggerated immune response to substances common in our environment.Atopic eczema is common 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 may evolve over time, requiring appropriate treatment at every stage of life, these diseases can be effectively managed with specific treatments and a healthy lifestyle.
In conclusion, although atopic diseases can persist into adulthood, early and appropriate management can often limit their impact on patients' quality of life and avoid long-term complications.