In all patients with eczema, breakdown of the protective top layer (the epidermis) leads to increased water loss from the skin.1,2 Failure of this barrier also allows the penetration of allergens across the skin from the external environment, e.g. pollens, house-dust mite products and microbes, and their interaction with cells of the immune system.1-3 Ultimately, an imbalance in the protective actions of the immune system and the inflammatory response arises, leading to the skin lesions associated with eczema.
Scratching to relieve the itching associated with eczema can actually make things worse, by increasing the breakdown of the epidermis and allowing the entry of certain types of bacteria across the skin, contributing to the allergic sensitisation and inflammation.4 In some people, allergens within the bloodstream, e.g. those from food, can also trigger an inflammatory response that appears as abnormal changes in the skin.5
Although tolerance of the immune system to the specific allergen usually develops, repeated contact can cause hypersensitivity, initiating further inflammatory responses.2 Additionally, a small proportion of people with atopy can develop immune responses against their own proteins within the skin, perpetuating the allergic inflammation.4
UK/GEN/16/0051 Date of preparation: October 2016