Systemic allergic contact dermatitis.
What is systemic contact allergic dermatitis?
Systemic contact dermatitis (SCD) or systemically reactivated allergic contact dermatitis (ACD) is a dermatitis/eczema that occurs when a person who is already sensitized to a substance through skin contact is exposed to that substance (allergen) via a systemic route. Exposure may be through oral, inhalational, injectable, and trans-mucosal routes.
Systemic contact dermatitis was first described in 1895 where individuals with a contact sensitivity to mercury developed dermatitis after systemic mercury exposure. Throughout the years many other allergens have been identified and the routes of exposure increased significantly.

What causes systemic contact dermatitis? …show more content…
Common allergens in cosmetics and skin care products that cause contact dermatitis
The most common allergen causing ACD is fragrance. More than 5000 different fragrances are used in cosmetics and skin care products. Seventy to eighty percent of fragrance allergy can be picked up by patch testing with Balsam of Peru and Fragrance Mix (which contains 8 common fragrances). Fragrance can also cause increased pigmentation of the affected skin, photodermatitis or contact urticaria.
It is important to know that "unscented" does not mean "fragrance-free". Some unscented products may contain a fragrance to mask other chemical odours. To indicate that no fragrance is added to a product it must be marked "fragrance-free" or "without perfume". Other common sensitisers (contact allergens) include preservatives, lanoline, p-phenyldiamine (dye) and an increasing number of herbal (plant) products.
Preservatives in cosmetics and skin care products are the second most common cause of skin reactions. Cosmetics that contain water must contain some preservative to prevent bacterial or fungal