Commonly used plant extract that can have potent antioxidant properties and some soothing properties. However, witch hazel’s high tannin content (tannin is a potent antioxidant) can also make it sensitizing if used repeatedly on skin. The bark of the witch hazel plant has a higher tannin content than the leaves. Producing witch hazel water by steam distillation removes the tannins, but the plant’s astringent qualities are what most believe give it benefit. [1, 2, 3]
Alcohol is added during the distillation process, the amount typically being 14–15%.  Witch hazel water is distilled from all parts of the plant; therefore, you never know exactly what you’re getting, although the alcohol content remains.
Depending on the form of witch hazel, you’re exposing your skin either to an sensitizing amount of alcohol or to tannins, or both. Moreover, witch hazel contains the fragrance chemical eugenol, which is another source of sensitivity. 
- Hughes-Formella B, Filbry A, Gassmueller J, Rippke F. skin-soothing efficacy of topical preparations with 10% hamamelis distillate in a UV erythema test. Skin Pharmacol Appl Skin Physiol. 2002;15(2):125-32.
- Choi H, Choi J, Han Y, Bae S, Chung H. Peroxynitrite scavenging activity of herb extracts. Phytother Res. 2002;16(4):364-7.
- Masaki H, Atsumi T, Sakurai H. Protective activity of hamamelitannin. J Dermatol Sci.. 1995;10(1):25-34.
- Thring T, Hili P, Naughton D. Antioxidant and potential skin-soothing activity of extracts and formulations of white tea; rose; and witch hazel. J Inflamm (Lond). 2011;8:27.
- Trüeb R. North American Virginian Witch Hazel (Hamamelis virginiana): Based Scalp Care and Protection for Sensitive Scalp; Red Scalp; and Scalp Burn-Out. Int J Trichology. 2014;6(3):100-103.