Anti‐inflammatory / anti‐oxidant activity of ingredients of sunscreen products? Implications for SPF

Abstract

ObjectiveThe Sun Protection Factor (SPF) of sunscreen products is derived from testing in vivo their ability to prevent erythema (“sunburn”). Recently, certain articles have raised concerns that sunscreen products may actively suppress erythema via anti‐inflammatory / anti‐oxidant (AI/AO) activity. These articles reason that this may result in a higher labelled SPF value than that provided by the efficacy of the UVR filters alone, giving consumers a “false sense of security”. On the other hand, since inflammatory processes are known to play a role in the mechanisms of photodamage / skin cancer induction and propagation, AI/AO activity may provide valuable incremental photoprotective benefit (provided that there is no interference with visible erythema). The objective of these studies, therefore, was to investigate the potential of AI/AO ingredients to suppress UVR‐induced erythemal response in human skin, in vivo.Methods In vivo studies with SPF30 sunscreen formulations containing a variety of AI/AO ingredients were performed according to the International Standard ISO24444:2010 method. While ISO24444:2010 requires assessment of erythema at 20 ± 4h post‐irradiation, an additional assessment at 5 h post‐irradiation was also used to determine potential delay in erythema development.ResultsNone of the formulations, containing a variety of AI/AO ingredients, influenced SPF determination in comparison to the vehicle formulation.ConclusionOur in vivo results demonstrate that commonly‐used AI/AO ingredients, at concentrations typically used in sunscreen products, neither influence SPF value nor delay erythemal response, i.e., the measured SPF reflects the true photoprotective capacity of the product.

Laboratory testing of sunscreens on the US market finds lower in vitro SPF values than on labels and even less UVA protection

“… 62 Other studies have found that these ingredients do not impact the measured SPF. 63 Ending our reliance on in vivo testing, and instead using laboratory tests that directly measure UV protection, 50 would dissuade manufacturers from adding ingredients solely to boost SPF values.…”

“…62 Other studies have found that these ingredients do not impact the measured SPF. 63 Ending our reliance on in vivo testing, and instead using laboratory tests that directly measure UV protection, 50 In 2007 and again in 2011, the US FDA refused to replace the human test with a measured UV absorption one over concerns that the substrates did not adequately mimic human skin and would not until data demonstrated equivalency. 28 This argument is centered on the false assumption of erythema being the only endpoint of health concern.…”

Safety and Photoprotective Efficacy of a Sunscreen System Based on Grape Pomace (Vitis vinifera L.) Phenolics from Winemaking

“…After sun exposure, there may be activation of acute and chronic inflammatory pathways. In this context, antioxidant and anti-inflammatory substances, without the UV filter properties in sunscreen, can also indirectly provide skin photoprotection [75].…”

Sunscreens Containing Cyclodextrin Inclusion Complexes for Enhanced Efficiency: A Strategy for Skin Cancer Prevention

“…Based on their mode of action, UV filters can be classified as (1) physical (inorganic) filters that reflect and scatter the light and (2) chemical UV filters that absorb the UVR (mainly UVB). The efficiency of UV filters is given by SPF value, indicating their ability to protect the skin against UVR; the higher the SPF, the better the sunburn protection [ 32 ]. While the maximum authorised concentrations of chemical UV filters in sunscreen formulations are usually reported at a range of 5–15% w / w of the formulation, physical UV filters could be added at higher concentrations (up to 25% w / w ) [ 33 , 34 ].…”