Anti-Pollution Matrix > Pollutants > Pollutant list > Pollen
Almost all plants that reproduce sexually produce sexual germ cells called pollen. The pollen grain is surrounded by a protective coating to resist physical and chemical stresses from the environment. This protective cover is composed of two layers. The outer layer (exine) gives the pollen grain its external shape and is composed of sporopollenin. Due to their small size (10-100µm) and light weight, pollen can stay in the air for long distances and thus fly several 100km. Pollen contains allergens that can cause seasonal hay fever (rhinitis allergica), bronchial asthma and other allergic reactions (irritated skin) in humans. Partly the pollen allergens are found in the pollen grain, partly they are localized on the surface of the pollen. Most of them are proteins or glycoproteins which are water-soluble and can penetrate the human skin or mucous membrane on contact. In the human body, these pollen proteins then act as antigens and could trigger an IgE-mediated immune response, skin aging or epidermal barrier disorders (1).
Impact on the skin
There are three potential areas of contact with the human body: the eyes, the nasal-mouth region, and the skin, although the focus here is on the skin.
Healthy, non-irritated skin provides adequate protection for most pollen. However, if the epidermal barrier of the skin is disturbed (dry skin, atopic dermatitis, ichthyosis) or if the skin is superficially damaged e.g. by small wounds, penetration of pollen allergens through the skin may occur under certain circumstances and an IgE-mediated allergic reaction may be triggered. Similar to other particulate contaminants (pollution), pollen can also affect the homeostasis of the skin and cause extrinsic aging effects. It is known that after the application of certain pollen proteins to the skin, a degradation of collagen structures can occur, induced by an increase in the concentration of the matrix metalloproteases MMP1 and MMP3. Likewise, after pollen application, inflammatory effects may occur due to an increase in the cytokine concentration of IL-1alpha and IL-8, and the epidermal barrier may be damaged (2,3,5).
Penetration of pollen allergens into the skin or hair follicles can be reduced by using various skin care products to strengthen or restore the epidermal barrier (4).
Detection methods of the effects
Penetration of allergenic pollen proteins into the skin has already been demonstrated in various in vitro and in vivo experiments using fluorescence laser scanning microscopy (LSM), which also showed penetration via the hair follicles into the dermis (5). Thus, hair follicles also represent a potential site for allergen penetration. In vitro 3-D keratinocyte models were used to determine various biochemical parameters (MMPs and interleukins), furthermore immunohistochemical and electron microscopic studies were performed to alter skin fine structures on ex vivo skin (5).
1) P.Sitte, H.Ziegler, F.Ehrendorfer, A. Bresinsky,: "Staßburger - Lehrbuch der Botanik". Gustav Fischer Verlag, Stuttgart New York, 33rd edition (1991).
2) Iwanaga T, Nioh A, Reed N, Kiyokawa H, Akatsuka H, A novel water-in-oil emulsion with a lecithin-modified bentonite prevents skin damage from urban dust and cedar pollen. Int J Cosm Science, (2020) 42, 229-236, DOI: 10.1111/ics.12605
3) Meinke MC, Patzelt A; Richter H, Schanzer S, Sterry W, Filbry A, Bohnsack K, Rippke F, Galecka J, Fölster-Holst R, Lademann J. Prevention of follicular penetration: barrier enhancing formulations against the penetration of pollen allergens into hair follicles. Skin Pharmacol Physiol, (2011) 24:144-150, DOI: 10.1159/000323018
4) Jacobi U., Engel K., Patzelt A., Worm M., Sterry W., Lademann J. Penetration of pollen proteins into the skin. Skin Pharmacol Physiol, (2007) 20:297-304, DOI: 10.1159/000108101
5) Kumamoto J, Tsutsumi M, Goto M, Nagayama M, Denda M, Japanese Cedar (Cryptomeria japonica) pollen allergen induces elevation of intracellular calcium in human keratinocytes and impairs epidermal barrier function of human skin ex vivo. Arch Dermatol Res (2016) 308:49-54, DOI: 10.1007/s00403-015-1602-y