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SD ALCOHOL 39-B.

Avoid / ASTRINGENT, SOLVENT, VISCOSITY CONTROLLING

SD Alcohol 39-B is a denatured alcohol primarily serving as a highly effective solvent in cosmetic formulations, facilitating the dissolution and dispersion of diverse ingredients. It additionally acts as an astringent, antimicrobial agent, and a penetration enhancer. While the CIR Expert Panel deems it safe for use within specific concentration ranges, its potential to induce dryness and compromise skin barrier function, particularly at higher concentrations, necessitates careful consideration.

Summary

Solvent Antimicrobial Astringent Penetration Enhancer Viscosity Controlling

Science

Mechanism of Action

SD Alcohol 39-B primarily functions as a solvent, efficiently dissolving and dispersing a wide array of cosmetic components, including surfactants, oils, dyes, and preservatives. On the skin, it exhibits astringent properties by contracting stratum corneum cells, which aids in tightening dilated pores and removing superfluous sebum. Moreover, it provides antimicrobial benefits by inhibiting bacterial growth and enhances the percutaneous absorption of other active ingredients.

Research

Clinical Evidence

High confidence
Effective range 0.05–70%
Optimal

N/A

Key findings

  1. 01 The Cosmetic Ingredient Review (CIR) Expert Panel has assessed SD Alcohol 39-B as safe for use in skincare and cosmetics at concentrations ranging from 0.05% to 12%.
  2. 02 Studies using SD Alcohol 40-B (a closely related denatured alcohol) demonstrated that a 12% concentration in a spray formula was non-irritating in a vaginal mucosal test on rabbits and did not induce photoallergy, dermal sensitization, or phototoxic responses in human subjects.
  3. 03 A 29% concentration of SD Alcohol 40-B in a gel formulation also showed no photoallergic, dermal sensitization, or phototoxic reactions in human subjects.
  4. 04 An irritation test in rabbits involving a 55.65% concentration of SD Alcohol 40-B produced only minimal effects.

Transparency

Dusting Analysis

Commonly dusted
Min. effective
12%
Red flag below
20%

SD Alcohol 39-B is often 'dusted' or criticized due to concerns regarding its potential to cause dryness, disrupt the skin barrier, and increase skin sensitivity. While concentrations up to 12% are generally considered safe by the CIR Expert Panel, formulations exceeding this threshold, particularly above 20% in leave-on products, are more likely to deplete natural oils, erode the skin's surface layer, and aggravate conditions like sensitive skin, eczema, or rosacea.

The Formula

Formulation

Solubility
Both
Optimal pH N/A
0 7 14

Stability

As an ethanol-based ingredient, SD Alcohol 39-B is readily miscible with both water and various organic solvents. It maintains stability under typical storage conditions and is characterized by a neutral pH. It is important to note its flammable nature.

Synergies

  • Enhances penetration of other active ingredients into the skin.

Conflicts

  • High concentrations can lead to skin dryness and irritation.
  • May erode the skin's surface layer, potentially weakening the skin barrier.
  • Can deplete natural oils, impacting skin hydration and integrity.
  • May aggravate sensitive skin conditions, including eczema, rosacea, and psoriasis.
  • Can increase skin sensitivity to external stressors and UV radiation.
  • As a penetration enhancer, it may increase the absorption of co-formulated irritants or potentially harmful substances.

Safety

Safety Profile

CIR Status
Safe as used
Max tested
70%
Sensitization risk Low

The Cosmetic Ingredient Review (CIR) Expert Panel determined SD Alcohol 39-B, along with other denatured alcohols, to be safe for use in cosmetic formulations in 2008. The denaturants t-butyl alcohol and diethyl phthalate were individually assessed and also found safe. While not formally 'FDA approved,' CIR's findings, which involve FDA participation, are widely recognized. However, despite this regulatory stance, concerns regarding its potential to cause dryness, disrupt the skin barrier, and increase skin sensitivity persist at higher concentrations.

Your Skin

Skin Compatibility

Yes Normal
No Dry
Yes Oily
No Sensitive
Irritancy Medium
Comedogenicity Unknown

Our Assessment

Verdict

Avoid

While recognized by regulatory bodies as safe within certain concentration ranges, SD Alcohol 39-B's inherent capacity to promote dryness and compromise skin barrier function, particularly at higher levels, positions it as an ingredient to avoid for precision skincare formulations aiming for optimal skin health, especially for sensitive or dry skin types.

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