What Is Oxyquinoline Sulfate?
Oxyquinoline Sulfate, also written as bis(8-Hydroxyquinolinium) sulphate, is a salt formed from two molecules of 8-hydroxyquinoline paired with sulfuric acid. The parent compound, 8-hydroxyquinoline, is derived from coal tar in its early history but today is produced synthetically through controlled chemical reactions that combine anilide intermediates with sulfuric and nitric acids, then refine the result into a high-purity powder. When neutralized with sulfuric acid, the material becomes the sulfate form used in cosmetics.
The antimicrobial ability of 8-hydroxyquinoline was noted in the early 1900s, which led pharmacists to explore it in topical antiseptics. As cosmetic regulations tightened, formulators adopted the sulfate version because it dissolves better in water based products and offers reliable preservation without the strong odor of older preservatives. Modern manufacturing involves reacting purified 8-hydroxyquinoline with diluted sulfuric acid, filtering, drying, then milling the crystals to a fine, beige powder that easily blends into creams, gels and lotions.
You can find Oxyquinoline Sulfate in a variety of leave-on and rinse-off items such as facial masks, anti-aging serums, light moisturizers, deodorant creams, scalp treatments and makeup where a gentle preservative boost is desired.
Oxyquinoline Sulfate’s Cosmetic Benefits/Uses
In skincare and beauty formulas this ingredient works in more than one helpful way:
- Antimicrobial: It slows the growth of bacteria, yeast and mold that can spoil a product. This keeps creams and gels fresh for longer and lowers the risk of skin irritation that can occur when microbes multiply in a jar or bottle.
- Chelating: It binds to metal ions found in tap water or raw materials. By trapping these metals it prevents color changes, rancid smells and a drop in preservative power, helping the overall formula stay stable and effective through its shelf life.
Who Can Use Oxyquinoline Sulfate
Because it is largely inactive on the skin’s surface and used at very low levels, Oxyquinoline Sulfate suits most skin types including oily, combination, normal and mature skin. Dry or easily sensitized skin can also tolerate it in well-formulated products because the ingredient itself is not known to strip moisture or disrupt the barrier. People with an existing allergy to quinoline compounds should avoid it, but that is rare.
The compound is synthetic and does not rely on animal-derived raw materials, so it is considered vegan and vegetarian friendly. Manufacturers typically confirm this status by checking their full supply chain for animal testing and animal by-products.
Current cosmetic safety assessments have not flagged Oxyquinoline Sulfate as a reproductive toxicant. In leave-on skincare it is used at very small concentrations, usually under 0.1%. Still, pregnant or breastfeeding individuals should consult a healthcare professional before adding any new product to their routine as a precaution. This is not medical advice.
The molecule does not absorb UV light and has no known photo-reactive groups, so it is not linked to photosensitivity. It also does not interfere with sunscreen actives or other common skincare ingredients, making it easy to slot into most routines.
Potential Side Effects/Adverse Reactions
Responses to topical Oxyquinoline Sulfate differ between individuals. The points below outline possible but unlikely reactions when the ingredient is used at the levels allowed in cosmetics. Most people will not notice any of these effects.
- Mild redness or stinging in those already sensitized to quinoline derivatives
- Localized contact dermatitis if used on broken or highly compromised skin
- Eye irritation if the product is accidentally rubbed into the eyes before it has set
- Rare allergic rash presenting as small itchy bumps
If any discomfort or visible reaction occurs stop using the product and seek medical advice if symptoms persist or worsen.
Comedogenic Rating
Rating: 0/5
Oxyquinoline Sulfate has no oily or waxy components, is used at very low levels and is water soluble, so it does not linger inside pores or create the kind of film that can trap dead skin cells. For these reasons it earns a zero on the comedogenic scale.
This makes the ingredient suitable for acne-prone or breakout-prone skin.
Because its main job is preservation rather than moisturizing, it is almost always paired with other ingredients that provide texture and hydration, so the overall formula—not the Oxyquinoline Sulfate itself—will determine if a product feels heavy on the skin.
Summary
Oxyquinoline Sulfate serves two core purposes in cosmetics: it curbs bacterial, yeast and mold growth to keep products fresh and it chelates stray metal ions to stop color shifts or foul odors. It performs both roles by chemically binding to microbes or metals, disrupting the factors that let them thrive.
You will not see it splashed across ads like hyaluronic acid or niacinamide. It sits quietly on the ingredient list of niche serums, masks and deodorants, valued by formulators who need a gentle preservative boost without adding greasiness or fragrance.
At the tiny concentrations allowed in skincare it is considered low risk for irritation, does not clog pores and has no links to long-term health concerns. As with any new product though, give your skin a chance to weigh in with a quick patch test before applying it all over.