Table 1.

Characteristics of the Studies Using Various Formulations of Hyaluronic Acid (HA) Alone for Improving Facial Skin Quality

Author, Year	Country	Hyaluronic Acid Formulations Used	Mode of Administration	Treatment Protocol	n	Age (Years)	Key Findings
Kerscher et al 200812	Germany	Stabilized HA-based gel of non-animal origin	Mid-dermal placement	Three treatment sessions 4 weeks apart	19	54±10	Skin elasticity and surface roughness improved significantly, and patient feedback was positive
Reuther et al 201013	Germany	Stabilized HA-based gel of non-animal origin	Micropuncture injections	Three treatment sessions four 4 apart	19	54±10	Significantly increased skin firmness and improved viscoelastic recoverycapacities
Streker et al 201314	UK	Stabilized HA-based gel of non-animal origin	Micropuncture injector device	Three treatment sessions 4 weeks apart	30	40–65	Overall skin quality was improved throughout the study and significant aesthetic improvements were observed
Sundaram et al 201815*	USA	Cross-linked HA	Multiple injections	Four sessions at 15-day intervals	24	35–55	Statistically significant improvements in skin surface topography and hydration in terms of moisture, tone/complexion, radiance, texture, uniformity, and global appearance
Hertz-Kleptow et al 201916	Germany	Cohesive polydensified matrix HA	Multiple injections	Three injections 4 weeks apart	25	36±5	Effective and safe for skin revitalization
Niforos et al 201917	France	Cross-linked HA gel	Intradermal injection	30 days and optional repeat treatment after 9 months	131	32–72	Safely and effectively improved skin smoothness and hydration
Ayatollahi et al 202018	Iran	Small particles of HA	Multiple injections	Three injections 3 weeks apart	20	40.15±6.63	Skin hydration increased, skin firmness was reduced, skin-tiring effect/fatigue was reduced, and skin elasticity increased
Kleine-Börger et al 202219	Germany	Small particles of HA	Microinjections	Microinjections 4 weeks apart	15	25–45	Significantly improved biomechanical viscoelastic skin properties
Nikolis et al 201820	Canada	Small particles of HA	Microinjections	Three injections 4 weeks apart	20	30–75	Significantly improved hydration
Hsieh et al 202221	China	Cross-linked HA	Microinjections	Three injections 4 weeks apart	8	35–50	Stimulated the production of collagen and other extracellular collagen components and restored the structural integrity of dermal microenvironment

Note: *Randomized controlled trials. All other studies were observational studies.

Abbreviations: HA, hyaluronic acid; UK, United Kingdom; USA, United States of America.