Irritation from products and skin sensitivity are common problems experienced by consumers globally. It’s important for formulators to understand the underlying causes and develop strategies to reduce these issues.
Sensitive Skin – Symptoms & Strategies
Sensitive skin is not a disease but a condition brought on by a reduced barrier function and nerve hypersensitivity. The hypersensitivity can be aggravated by external factors such as cold, heat, wind and UV exposure, or by internal factors, like stress or disease. The symptoms of sensitivity, such as redness, itching, stinging/burning and inflammation, have different and often overlapping mechanisms that may be addressed as follows:
- Itching can be treated with antihistamines.
- Redness can be treated with materials that inhibit interleukin 1 alpha and PGE2.
- Burning/stinging reactions can be reduced using materials that inhibit or block the TRVP thermo neuro receptor.
- Inflammation is moderated primarily by interleukins, lipoxygenase, and prostaglandins.
Use these strategies to improve barrier function:
- Use emollients that increase hydration, reduce TEWL, and modify skin lipid crystallinity, like isopropyl isostearate (EU) and isostearyl isostearate (EU).
- Formulate your product at a PH of around 4-4.5. This helps the formation of epidermal lipid bilayers and assists in preserving the formulation.
- Use materials that protect and/or promote barrier repair:
SymRepair® 100 (EU) (Hexyldecanol, Bisabolol, Cetylhydroxyproline Palmitamide, Stearic Acid, Brassica Campestris (Rapeseed) Sterols) by Symrise
Niacinamide (EU)
L-Lactic acid (EU) was shown to increase stratum corneum ceramide levels by 38% when applied to the volar forearm twice a day for four weeks. - Use emulsifiers that don’t disrupt barrier function:
Lecinol S-10 (hydrogenated lecithin) by Nikkol Chemical is derived from soy lecithin and contains 25 – 30% phosphatidyl choline
Emulmetik™ 300 (EU) (lecithin, 23% phosphatidyl choline) by Lucas Meyer
Emulgade® PL 68/50 (EU) (cetearyl glucoside, cetearyl alcohol) by BASF
Recommended Materials that Block TRVP Receptor
- Noraplex (nopal cactus extract) by Barnet is a TRPV-1 antagonist that reduces neurosensory-induced irritation. Noraplex stabilizes membrane channels responsible for calcium transport, which then blocks the initiation of the inflammatory response. A clinical stinging test was conducted on 20 subjects with sensitive skin. Lactic Acid 8% was applied to the nasal fold area in an untreated control group, a Noraplex 5% group, and a Noraplex 3% group. Stinging severity was rated with the 0 to 4 neurosensory irritation (NSI) score over 30 minutes. Noraplex reduced the irritation compared to the control group, for both the 5% (66% less) and 3% Noraplex (48% less) groups with p<0.05. It was also shown to significantly reduce methyl nicotinate induced irritation.
- SymSitive® 1609 (EU) (Pentylene Glycol and 4-t-Butylcyclohexanol) by Symrise is an active ingredient for treating sensitive skin. It has been shown to reduce capsaicin-induced burning/stinging, calm over-reacted skin, and increase skin’s tolerance to physical stimuli.
Recommended Materials with Antihistamine Activity
- CP Oat Avenanthramides (glycerin, aqua/water, oat extract) by Oat Services Limited is a 1:1 glycerin-water mixture containing 110 ppm actives (avenanthramides AF-1, 2, and 6). Significant anti-inflammatory activity has been seen at levels as low as 1 ppm active in formulations.
- SymCalmin® (EU) by Symrise is an anti-irritant/anti-itch active. It is sold as a 50,000 ppm solution of dihydrovenanthramide D in butylene glycol/pentylene glycol. Avenanthramides A, B, and C are the compounds in oats that are responsible for its soothing properties. (Avenanthramides are amides of cinnamic and anthranilic acids).
Recommended Materials to Reduce Redness/Erythema
- SymRelief® S (EU) (bisbolol and hydroxymethoxyphenyl decanone – common name paradol) by Symrise is a synergistic, active blend that claims to provide a visible reduction in skin redness and blotchiness in only 1 day. 2% SLS-induced skin irritation was reduced by 59% after 3 days of using a formulation containing only .0657% SymRelief S. It has also been shown in vitro to be an effective inhibitor of IL-1α, TNFα, COX-2 and PGE2. Additionally the material is a potent antioxidant.
Recommended Materials with Anti-Inflammatory Activity
- A lotion containing 3% Canadian Willowherb™ Extract (EU) (5% solids) by Lucas Meyer Cosmetics was shown to have similar anti-inflammatory activity compared to a 1% hydrocortisone lotion.
- Lipex® Cellect (EU) (phytosteryl canola glycerides) by AAK Lipids contains 30% canola-based phytosterols and has previously been shown to have anti-inflammatory activity.
- Gorgonian Extract BG (butylene glycol and sea whip extract) by Lipo Chemical contains pseudopterosins extracted from sea whip, which have been shown to have significant anti-inflammatory activity at levels as low as .02% active. Vasodilation was significantly reduced using ethyl nicotinate as a model irritant.
- Ronacare® Troxerutin (trihydroxyethyl rutin) by EMD is a water-soluble, stable bioflavonoid produced by ethoxylating Rutin. Troxerutin has been shown to significantly inhibit prostaglandin formation.
- NET STG (stearyl glycyrrhetinate) by Nikko Chemicals.
- D Panthenol by DSM.
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