How safe is Hyaluronic acid in cosmetics? Hyaluronic acid is a glycosaminoglycan found in connective tissues and extracellular matrix and also used as a dermal filler. A 70kg man has an average of about 15 grams of hyaluronic acid in their body where it is constantly recycled everyday, Hyaluronic acid is also found in the extracellular capsule of Group A streptococcal where it predominates virulence in humans thereby making human susceptible to viral attacks. Hyaluronic acid is highly implicated in its significant contribution to cellular proliferation and migration thereby contributes to progression of some malignant tumours[1] Hyaluronic acid serves as a tumour marker for prostate and breast cancer and therefore use to monitor the progression of these cancers also Hyaluronic acid levels correlates with poor prognosis and malignancy in some cancers.[2] It has been noted that hyaluronic acid facilitates cancer metastasis through the molecules it stimulates and interacts with in the human body [3] ;molecules such as hyaluronic acid synthase; CD44 and EMT(Epithelial-mesenchymal transition) amongst others. Hyaluronic acid used in cosmetics comes in three forms which are : -High molecular weight (HMW) hyaluronic acid(1000-1400 kDa) -Medium molecular weight hyaluronic acid -Low molecular weight hyaluronic acid (20-300kDa) High molecular weight hyaluronic acid works only on the surface of the skin where it provides hydration to the skin;prevent trans-epidermal water loss and scavenge free radicals. While the high molecular weight hyaluronic acid showed some benefits ;the low molecular weights hyaluronic acid triggers skin inflammation and with too much inflammation ;ageing process will be set in. Hyaluronic acids cannot penetrate deep into the skin where it is most needed unless is broken into small pieces which comes with the side effects of inflammation. References: 1. Stern, edited by Robert (2009). Hyaluronan in cancer biology (1st ed.). San Diego, CA: Academic Press/Elsevier. ISBN 978-0-12-374178-3. 2.Gritsenko PG, Ilina O, Friedl P (2012). "Interstitial guidance of cancer invasion". J. Pathol. 226 (2): 185–199. doi:10.1002/path.3031. PMID 22006671. 3.Bharadwaj AG, Kovar JL, Loughman E, Elowsky C, Oakley GG, Simpson MA (2009). "Spontaneous metastasis of prostate cancer is promoted by excess hyaluronan synthesis and processing". Am. J. Pathol. 174 (3): 1027–36. doi:10.2353/ajpath.2009.080501. PMC 2665762. PMID 19218337.