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ALLERGIES
Allergens - The main contact allergies
The organism is defended by the immune system, which reacts to any foreign body, the allergens, by developing a whole serie of substances called immunoglobulins, as well as activating immune cells, such as the Langerhans cells. The immune system remembers the "allergen", which triggered the immune response, and the second reaction to this same allergen will be more rapid and more effective.
In an allergic response, there is hypersensitivity so that during later encounters with the allergen, the reaction is by far too violent and provokes itching, skin redness, a runny nose, respiratory difficulties (asthma), stomach pains, or headaches.
 Allergens
The various allergens that could cause an allergic skin reaction are:
insect venoms, particularly from bees and wasps, which cause swelling, redness and itching. In certain cases of hypersensibility or multiple simultaneous stings anaphylactic shock can occur, i.e. a violent allergic reaction which requires emergency treatment.
The second most frequently encountered allergens are cat and dog hairs, together with those of rabbits, guinea pigs and hamsters and bird feathers. The symptoms are mainly asthma or a skin irritation. Then come moulds which provoke allergies affecting the nasal airways as well as causing skin irritations.
Locally or systemically drug admistering can cause allergic skin reactions in the form of redness, e.g. allergies to penicillin or to aspirin. Some metals (nickel, chrome, molybdenum) may also cause allergies. Nickel is particularly important as it is used in the composition of coins, dress jewellery for example.
To diagnose sensitivity to different allergens, doctors carry out sensitising skin tests. Small doses of allergens are applied on the skin, which trigger a skin reaction (or otherwise) .
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The main contact allergies
Contact eczema is an allergic reaction to household cleaning products, synthetic materials and metals. Symptoms appear 24 to 72 hours after contact with the substance: the skin swells, becomes red, itches ; blisters and scabs form. The eczema is first of all local but then may extend to the whole body.
Urticaria is a reaction characterised by a skin rash. The skin regains a completely normal appearance after hours to days. Allergens such as pollens, animal Hair, foods and drugs are substances capable of causing urticaria.
Atopical dermatitis indicates hereditary allergic sensitivity appearing from early infancy and disappearing commonly in adulthood. The substances responsible are particularly dust, mites and pollens as well as certain foods (eggs, milk, soya etc.).
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