Itching: Understand better with our experts
Attached to the Civic Hospices of Lyon
« It is a very recurrent symptom, that we experience at any age during life. During a consult, we meet as many as babies with eczema than elderly persons with a very itchy dry skin. Itchings may be temporary or permanent, sometimes restricted or affecting all the body. This symptom, a bit global, correspond to very different situations and the stake is to understand what is the cause of it.»
BIODERMA Scientific Director
This chronical inflammatory dermatitis alternates by flare-ups periods and calm. The cutaneous barrier, with recurrent lack of filaggrin, causes a severe skin dryness associated with excessive immune reactions.
It is a reaction caused by allergen contact with the skin. Jewellery, clothes, cosmetics or medicine make the skin sensitive and prone to itchings.
It is characterised by red plates very itchy linked to a direct allergen contact with the skin, an immune answer with food, or an insect bite.
This chronical inflammation often has a genetic origin which affects 2% of the population. It is characterised by an increase of the epidermis cells proliferation and occurs by scale lesions.
For people aged more than 65 years old, the lack of lipids may cause an itching sensation and discomfort.
That's Senile Xerosis, also called Senile Pruritus. It affects 60% of elderly persons.
BUT NOT ONLY!
Michèle Sayag explications, Allergist Doctor.
• The pruritic pathways of urticaria and contact eczema go through the immune cells: they release mediators (histamine, substance P, serotonin, some proteases et cytokines), which activate the nerve fibres. Antihistamines stop or reduce itching by blocking histamine receptors but they are ineffective on other types of itching.
Apart from the well-known role of histamine in pruritus during urticaria, scientists have pointed out the existence of 2 news pruritic pathways, involving specific neurotransmitters, on which it is interesting to act to reduce the sensory nerve fibres activation that transmits the pruritus signal to the brain.
In Atopic Dermatitis, the pruritic pathway involves keratinocytes, superficial cells of the skin that release TSLP, which itself activates the sensory nerve fibres.
In Psoriasis, it is the NGF produced by keratinocytes that activates these same fibres.
• The mechanism is different in the cutaneous dryness due to skin ageing (or Senile Xerosis). The sensory nerve fibres activation necessarily occurs, but the pruritic path remains poorly understood. Most likely, it involves the alteration of the cutaneous barrier, specific to the skin ageing.