Booster No5 contains Menadione (Vitamin K3).
According to Dr. Masuda (and colleagues) from the Shiseido Research Centre, dark circles under the eyes form as a result of poor blood flow. Researchers have found that in the area of dark circles, blood flowed at a slower rate compared to the area in the cheeks. They also found more melanin production in subjects with dark under-eye circles.
Dr. Tsuyoshi Mitsuishi, the lead investigator, reported an improvement in dark under-eye circles in participants who used a topical application that contained vitamin K.
People apply vitamin K to the skin to remove spider veins, bruises, scars, stretch marks, and burns. It is also used topically to treat rosacea, a skin condition that causes redness and pimples on the face. After surgery, vitamin K is used to speed up skin healing and reduce bruising and swelling.
The irritation feeling might come from effect of Vitamin K reinforcing the blood flow under the eyes and forcing any coagulated blood to flow away.
EVENSWISS® products are formulated to avoid the use of ingredients commonly known to be irritating or allergenic, however it would be impossible to anticipate all ingredients that might provoke an allergic or irritating reaction in some users.
In order to avoid, as much as possible, these kinds of reactions it is important to use boosters together with a base or other cream in the ratio recommended in EVENSWISS® instructions. In cases of hypersensitivity EVENSWISS® recommends combining the booster in a 1:20 ratio to bases or other creams instead of 1:10.