37
J. Cosmet. Sci., 75.1, 37–48 (January/February 2024)
*Address correspondence to Michael Pirrung, Michael.pirrung@ucr.edu
The Fallacy of Hyaluronic Acid Binding a Thousand Times its
Weight in Water
SCOTT BORCHERS AND MICHAEL C. PIRRUNG
Department of Chemistry, University of California, Riverside, California, USA (S.B., M.P.)
Department of Pharmaceutical Sciences, University of California, Irvine, California, USA (M.P.)
Accepted for publication January 01, 2024.
Synopsis
This study re-examined experimental reports and past literature of water binding by the humectant
hyaluronic acid, in comparison with another common humectant, glycerol, to critically evaluate the common
claim that hyaluronic acid binds a thousand times its weight in water, making it especially suited to be
a cosmetic moisturizer. Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC)
were used to study aqueous solutions of glycerol and hyaluronic acid. A 0.1 weight %aqueous solution of
hyaluronic acid (the putative 1,000 times its weight) is a clear, flowing liquid, comparable to a 10 weight %
aqueous solution of glycerol. The melting point and melting heat of fusion of the hyaluronic acid solution were
indistinguishable from pure water, while both were reduced for the glycerol solution. This is as expected, as
colligative properties of aqueous solutions are proportional to concentration, and the polymer is at a much
lower molar concentration than glycerol. There is imperceptible freezing point depression by hyaluronic
acid, whereas that by glycerol is as expected. No experimental evidence was found for any special ability of
hyaluronic acid to bind water at the claimed level of a thousand times by weight. The origin of the fallacy that
it binds water at that level can be traced to older literature that has been misunderstood for the meaning of
binding, as compared to other physical properties such as hydrodynamics.
INTRODUCTION
Hyaluronic acid (HA) is a natural carbohydrate polymer that is a major component of the
human extracellular matrix. It is known for diverse physiological roles, including as the
lubricant in synovial fluid. In the form of a more widely available bacterial version, HA is
used as a humectant which enhances the water-holding capacity of the skin, in personal
care and cosmetic products, inter alia. Water is essential to normal skin function, and its
retention by the stratum corneum is facilitated by natural hygroscopic agents, including the
two compounds studied here, hyaluronic acid and glycerol.1 They enhance water absorption
from the dermis into the epidermis, and are also believed to aid absorption of ambient
water by the stratum corneum in humid conditions.2 Thus, the ability of a humectant to
bind water is intrinsic to its utility in cosmetic products, which gives this work its interest
to the cosmetic industry.

38 JOURNAL OF COSMETIC SCIENCE
The moisturizing power of HA is widely renowned, and many claims appear in various
media that HA binds vast amounts of water. Statements that it can bind over one thousand
times its weight in water are common, including in peer-reviewed literature (“The unique
helical coil conformation of HA allows it to trap up to 1,000-fold of its weight in water”3,
“it retains up to 1,000 times its weight in water”4). Similar statements are attributed to
dermatologists (“HA binds to one thousand times its weight in water”5), including renowned
academics (“it is capable of binding over one thousand times its weight in water”6). Some
commercial product sites make a grander claim that a gram of HA binds 6 L of water (“one
gram of hyaluronic acid can hold six litres of H
2 O”7, “a single gram of hyaluronic acid has
the impressive ability to hold up to six (yep, six) litres of water”8). These examples portray
HA as the ultimate moisturizer.
This work critically examines the binding of water by HA in both literature and experimental
studies and dispels the notion that it has such remarkable power. Its properties are also
compared to a more conventional humectant, glycerol. A thread is traced to early studies
that could have led to the misimpression that HA has such tremendous water binding
properties.
BACKGROUND
One potential source of the belief in the great ability of HA to bind water comes from a
review article by Sutherland which states, “the water-binding capacity correlates with the
molecular mass and can be up to six litres of water per gram of polysaccharide.”9 However,
data to support this statement are not found in this article, and neither is a citation to any
literature that made such a measurement. That review might be the original spur for many
subsequent erroneous claims. Citing to this paper, Becker states, “one gram of hyaluronic
acid can hold up to 6 L of water.”10 While Jegasothy asserts “it can attach and hold large
amounts of moisture approximately 6 L of water in just 1 g”11, no citation to literature nor
measurement of this property can be found in this publication. Olejnik et al. state “1 g
of HA retains 6 L of water” without literature citation, but likely based on Sutherland’s
comment.12 With water’s density of 1 g/mL, it is also worth noting these statements can
be read to mean that HA binds 6,000 times its weight in water, not the 1,000 times more
commonly claimed. Our review of this literature has not found a basis for this change
perhaps later authors were simply motivated to make a more conservative claim.
Several past DSC studies of solutions of HA of various molecular weights have been reported.
The DSC method varies the temperature and measures the heat evolved/consumed as solid-
liquid phase transitions occur. However, these studies were of much more concentrated
solutions than studied here, approximately 1:1 w/w. This enabled observation by DSC of
phase transitions of the different types of water molecules in those solutions. These include
non-freezable bound waters, freezable bound waters, and free waters. Non-freezable water
refers to water that is directly bound to the polysaccharide rather than free in solution,
where it would be available to interact normally with other water molecules and exhibit
conventional behavior, including freezing at the normal temperature. There may also be
freezable water associated with the polysaccharide that freezes at a lower temperature. At
the low concentration of HA studied in this work, these two types of bound water are
also at low concentration and therefore imperceptible by DSC because it measures a bulk
solution property.