What Is Potassium Isosteareth-2 Phosphate?
Potassium Isosteareth-2 Phosphate is the potassium salt form of isosteareth-2 phosphate, a molecule created when fatty alcohols derived from isostearic acid are reacted with phosphoric acid and then neutralized with potassium. The result is a water-loving, oil-loving ingredient that behaves much like a gentle soap. It emerged in the 1990s as formulators looked for milder, more skin-friendly cleansers to replace harsher sulfates. Production starts with plant-based or synthetic isostearic acid, which is turned into a short-chain ethoxylated alcohol (isosteareth-2). This alcohol is then phosphorylated and finally neutralized with potassium hydroxide, giving the finished powder or liquid used by cosmetic labs.
You will most often spot Potassium Isosteareth-2 Phosphate in face cleansers, micellar waters, cleansing balms, shampoo, body washes and makeup removers. It can also appear in multi-tasking products like exfoliating masks or hydrating lotions where a light cleansing action is desired without stripping the skin.
Potassium Isosteareth-2 Phosphate’s Cosmetic Benefits/Uses
This ingredient is prized for one main job in skin and hair care products.
As a cleansing agent it lowers the surface tension of water, helping oils, dirt and leftover makeup mix with water so they rinse away easily. Because it is milder than many traditional surfactants, it leaves the skin feeling comfortable rather than tight or squeaky. In shampoos it helps lift sebum and styling residue without roughing up the cuticle, which supports smoother, shinier hair.
Who Can Use Potassium Isosteareth-2 Phosphate
Because it is a mild cleansing agent that rinses away without leaving a heavy film, Potassium Isosteareth-2 Phosphate is generally well tolerated by all skin types, including oily, combination, dry and even sensitive skin. Those with very reactive or compromised skin should still monitor how their skin feels, as any surfactant can cause discomfort if used in a formula that is too strong or applied too often.
The ingredient is synthesized from plant derived or laboratory made raw materials and contains no animal by-products, so it is considered suitable for both vegans and vegetarians.
Current safety data show no specific risks for pregnant or breastfeeding women when the ingredient is used topically in rinse-off or leave-on products at normal cosmetic levels. This is not medical advice and anyone who is pregnant or nursing should run any skincare product past a qualified healthcare professional to be on the safe side.
Potassium Isosteareth-2 Phosphate does not make skin more sensitive to sunlight, so it is not regarded as a photosensitizer. Normal daily sun protection practices are still recommended.
Potential Side Effects/Adverse Reactions
Topical reactions to Potassium Isosteareth-2 Phosphate vary from person to person. The points below list potential side effects, yet most people will not experience them when the ingredient is used at typical cosmetic concentrations in a well formulated product.
- Mild skin irritation such as redness or stinging
- Dryness or tightness if the overall formula is not adequately balanced with moisturizers
- Eye irritation if the product accidentally gets into the eyes
- Rare allergic contact dermatitis in individuals sensitive to phosphate or ethoxylated compounds
If any discomfort, persistent redness, swelling or itching occurs while using this ingredient or a product that contains it, discontinue use and consult a healthcare professional.
Comedogenic Rating
Rating: 0–1 (very low)
Potassium Isosteareth-2 Phosphate is a small, highly water-soluble cleansing agent that rinses off cleanly and does not linger in pores to mix with sebum or create blockages. It lacks the heavy, waxy structure seen in ingredients that typically trigger clogs, so the likelihood of it causing comedones is minimal. Because of this low residue profile it is generally suitable for people prone to acne and breakouts.
Since it usually appears in rinse-off products, exposure time on the skin is short which further reduces any comedogenic risk. If it is used in a leave-on formula, the overall product composition and concentration will matter more than the ingredient itself.
Summary
Potassium Isosteareth-2 Phosphate is a mild surfactant that lifts oil, dirt and makeup by lowering water’s surface tension and pairing with both water and oil so debris can be washed away. It delivers this cleansing action without the harshness associated with stronger sulfates which helps skin and hair feel comfortable after use.
While not the most talked-about ingredient on social media it has a steady presence in gentle cleansers, micellar waters and lightweight shampoos where formulators want mild yet effective cleansing. Its plant-derived origins and vegan status add to its appeal for brands focused on cleaner formulations.
Current safety data show it to be low risk when used at normal cosmetic levels with only rare reports of irritation or allergy. As with any new skincare product a simple patch test is a smart precaution to make sure your skin agrees with the full formula.