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Atopic dermatitis (AD)
formerly known as " atopic dermatitis " "genetic allergic dermatitis", is a chronic inflammatory skin disease related to genetic allergic diathesis. , manifesting as itching, polymorphic skin lesions with a tendency to ooze, often accompanied by asthma, allergic rhinitis, etc., and is the "number one disease" in dermatology.
Many patients always ask three "whys" after being diagnosed with AD:
Q1
"Why are skin allergies prone to allergies from birth?"
Q2
or "Why didn't I have allergies when I was a child, but now I have them?"
Q3
and "Why do I have them all over again?" Can’t get rid of the root cause?”
Let’s talk about the pathogenesis of AD. Before defeating this number one disease, we must know ourselves and our enemies. In general, the causes of AD are very complex, and genetic and environmental factors are both involved in the occurrence of the disease. In just a few minutes of medical consultation, it is difficult for the doctor to fully describe the causes of the disease to the patient, but if you carefully consider the doctor's consultation, you will find that the answer is hidden in it.
Confidant Chapter
The mother of the patient: My child has had repeated allergies since he was a child. What is the reason?
Doctor: Do you or your child's father have any other allergic symptoms or diseases such as eczema, allergic rhinitis, or allergic asthma? Mother of child with
: Yes! The child's father suffers from allergic rhinitis, and I am allergic to shrimp.
Atopic dermatitis The "atopic" actually means allergic constitution. AD has an obvious familial genetic tendency. Foreign studies have found that if one parent has AD, the probability of offspring developing AD is 59%; if both parents have AD, the rate rises to 81%. For example, children of parents who suffer from allergic rhinitis, asthma and other allergic diseases are more likely to develop AD.
Scientists have confirmed the existence of a variety of susceptibility genes related to the onset of AD. Some of them control the immunity and metabolism of the skin, and some determine the integrity of the skin barrier. When these genes are missing or abnormal, AD may occur. . For example, AD patients will have dry and flaky skin, which may be due to mutations in the filaggrin gene that protects skin integrity.
In addition, AD patients often have immunological abnormalities. This is not what we usually call "decreased immunity", but changes in a variety of immune cells and factors, causing the immune environment to lose balance and develop in the direction of "allergy" .
Under the influence of a variety of genes and immune factors, the protective effect of the skin barrier is weakened, the immune system becomes disordered, and dermatitis and itching ensue.
Knowing the other
Guy: I haven’t had many allergies since I was a child. No one in our family has had dermatitis or eczema. Why do I still get this disease?
The young man’s girlfriend: Yes, the doctor also said that I have atopic dermatitis and I itch terribly every day. Did he pass it on to me? Doctor
: Atopic dermatitis is not contagious, but its incidence is getting higher and higher now. In addition to personal physical factors, it also has a lot to do with the external environment.
Here we will mention the external causes of AD, which mainly include changes in living environment and lifestyle, disorders of skin flora, and transcutaneous sensitization to allergens.
01 "Hygiene hypothesis" and bacterial imbalance
In the past 30 years, people's living environment (climate, air pollution, etc.) and lifestyle have changed dramatically, and the incidence of AD has increased rapidly. In developed countries, the prevalence of AD among children has even As high as 10%~20%. A survey conducted in Shanghai in 2012 found that the prevalence of AD in cities was significantly higher than in rural areas. As early as 1989, foreign scholars proposed the "hygiene hypothesis", that is, if children continue to live in an overly hygienic environment in early childhood and are less exposed to various pathogens (such as parasites, viruses, bacteria, etc.), they will be more likely to develop diseases. Allergic diseases.
There are hundreds of millions of microorganisms in human skin and intestines. They coexist harmoniously and balance each other to form a microbial community (flora) that maintains human health and stability.When the integrity of the skin barrier is damaged, such as excessive cleaning of the skin, excessive scratching, or the abuse of antibiotics destroys the balance of the flora, then the number of "good" bacteria will decrease, and the "bad" bacteria will cause trouble, and the body's The balance is disrupted and disease ensues.
02 Allergens
Allergens are one of the important factors in the pathogenesis of AD. If AD is suspected, the doctor will recommend that the patient undergo an allergen test. A considerable number of patients can detect specific allergens, such as dust mites, pollen, milk, egg albumen, etc. Allergens enter the body through the damaged skin barrier, causing allergic reactions (also called allergic reactions), which may lead to recurrence and exacerbation of skin itching and eczema. If you live in an environment exposed to allergens for a long time, the rash will recur. allergen detection helps AD patients discover or clarify suspected allergens, so as to prevent them in a targeted manner.
But not all AD patients can detect allergens, because a small number of them belong to "endogenous AD", which is mainly related to the immune environment in the body.
What you need to know is that internal genetic factors and external environmental factors are not independent of each other. They will also affect each other. Under the combined effect of genetics and environment, the immune balance of the skin is broken, which is the main cause of AD. reason.
AD is a chronic skin disease that often lasts a lifetime. Only by knowing ourselves (heredity) and the enemy (environment), and understanding the pathogenesis of AD, can we prevent and treat it in a more targeted manner, and can we defeat it more calmly.
[Reference]:
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[1] Atopic Dermatitis Collaborative Research Center of the Immunology Group of the Dermatology and Venereology Branch of the Chinese Medical Association. Chinese Guidelines for the Diagnosis and Treatment of Atopic Dermatitis (2020 Edition)[J]. Chinese Journal of Dermatology, 2020, 53(2):81-88.
[2]Lisa B. Zaoutis, Vincent W. Chiang. Comprehensive pediatric hospital medicine[M]. Philadelphia: MOSBY ELSEVIER, 2007: 981-990.
[3] Luo Jincheng, Song Zhiqiang. The pathogenesis of atopic dermatitis [J]. Chinese Journal of Clinical Immunology and Allergy, 2017, 11( 4):375-381.
Content source:
Authorized reprint from the "Human Defense Assistant" WeChat public account
