By Dr Ananya Mandal, MD
The exact cause of atopic dermatitis is not known. However, the Pathophysiology that underlies the condition is known to be complex. Severe genetic and environmental influences have been shown to play a role in causing and flare ups of atopic dermatitis.
The genetic basis of atopic dermatitis is strengthened by the fact that infants of parents who were or are affected by the condition are more likely to suffer from the condition than other infants.
This risk is further raised when one of the parents has other allergic or immunological conditions like asthma or allergic rhinitis. This suggests that the genes linked to these disorders are also linked to atopic dermatitis.
There are studies that show that specific genetic mutations in the IL-4 receptor region results in increased levels of IgE are also linked to atopic dermatitis.
High levels of serum IgE are an element that differentiates atopic dermatitis from other forms of dermatitis. High IgE stimulates eosinophils and mast cells to release pro-inflammatory cytokines leading to inflammation.
There are also possible defects in monocytes and Langerhans cells. These cells play an important immunologic role in the skin that lead to increase and overwhelming immune and inflammatory responses.
These cells may also react to environmental allergens like dust mites, animal dander, certain foods, weeds, molds, bacteria. These are known triggers that lead to flaring up of atopic dermatitis.
In atopic dermatitis abnormally dry skin is a primary clinical finding. This happens when there are defects in lipid production.
Particularly there are defects in ceramide production in the stratum corneum. Low ceramide content leads to damage to the permeability barrier of the stratum corneum that leads to loss of moisture and water. Excess water loss from skin leads to drying and cracking of skin.
Some of the common environmental triggers that stimulate flare up of atopic dermatitis include allergens. These allergens are substances that can cause the body to react abnormally or give rise to allergic reactions.
Some of the most common allergens that can cause atopic dermatitis include:-
Animal dander or pet fur
House dust mites
Food allergens for example eggs, cow’s milk, nuts, soy, wheat etc. Food allergies are seen in two thirds of cases of atopic dermatitis and having a food allergy raises the likelihood of getting atopic dermatitis.
Exposure to tobacco smoke or air pollutants and hard water may trigger atopic dermatitis flare ups.
There are other environmental triggers for atopic dermatitis as well. These do not cause allergic reactions due to a specific allergen. Some of these include:-
Harsh soaps that remove the layer of moisture and oils from the skin leaving it dry. Excessive washing and exposure to water and soaps also leads to similar reactions.
Cold weather may aggravate the condition while summers may resolve the symptoms.
Friction from rough clothing.
Hormonal changes in women during their menstrual cycle may also trigger bouts of atopic dermatitis. Some women have a flare-up of their atopic dermatitis in the days before their period. Similarly rise of female hormones during pregnancy may make atopic dermatitis worse in around 50% of susceptible women. A quarter of women however may find their symptoms of atopic dermatitis improving during pregnancy.
Stress is likely to be associated with atopic dermatitis.
Vigorous exercise with excessive sweating may trigger a flare up of eczema.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)