What Is Isotridecyl Phosphate?
Isotridecyl Phosphate is the cosmetic name for phosphoric acid esterified with isotridecyl alcohol, a branched chain alcohol that has thirteen carbon atoms. The result is a clear to pale yellow liquid that acts like a mild surfactant. Although the alcohol portion can be sourced from petrochemicals or plant oils, the finished ingredient is fully synthetic so it can meet strict purity and safety standards.
The use of phosphate esters in personal care dates back to the mid 20th century when formulators looked for gentler alternatives to harsh soaps. As research advanced, branched alcohols such as isotridecyl alcohol proved especially good at producing stable, skin-friendly phosphates. By the 1990s Isotridecyl Phosphate was appearing in both salon and mass-market products because it gave brands a way to cleanse the skin without stripping its natural barrier.
Manufacturing involves reacting phosphoric acid with isotridecyl alcohol at controlled temperatures, then neutralising and purifying the mixture. This process, called esterification, yields a molecule with both water-loving and oil-loving parts, which is why it can mix ingredients that would otherwise separate.
You will most often see Isotridecyl Phosphate in facial cleansers, micellar waters, shampoos, body washes, lightweight lotions, sunscreens, scalp treatments and makeup removers. It can also appear in leave-on emulsions such as serums where it helps keep the formula uniform over time.
Isotridecyl Phosphate’s Cosmetic Benefits/Uses
In formulas Isotridecyl Phosphate wears two main hats, each bringing its own set of perks:
- Cleansing: Its surfactant nature loosens dirt, oil and makeup so they rinse away easily, which leaves skin and hair feeling fresh yet comfortable
- Emulsifying: It helps water and oil blend smoothly, giving products a consistent texture and preventing separation throughout their shelf life
Who Can Use Isotridecyl Phosphate
This ingredient is generally well tolerated by most skin types, including normal, oily, combination and sensitive skin. People with very dry or eczema-prone skin might find frequent use of any surfactant slightly drying, so a richer follow-up moisturizer is advised.
Isotridecyl Phosphate is made without animal-derived materials, so it is suitable for vegetarians and vegans. The starting alcohol can come from petrochemical or plant sources but either way no animal inputs are involved.
Current data shows no specific risks for pregnant or breastfeeding women when the ingredient is used at normal cosmetic levels. That said this is not medical advice and anyone who is pregnant or nursing should clear all skincare products with a healthcare professional first to be safe.
The molecule does not absorb UV light or make skin more reactive to sunshine, so it is not considered photosensitizing. It also plays well with most other cosmetic actives, which is why it shows up in many multi-benefit formulas.
Potential Side Effects/Adverse Reactions
Individual responses to topical Isotridecyl Phosphate vary. The points below outline potential side effects but most people will not experience them when the ingredient is used correctly in a finished product.
- Mild transient stinging if applied to broken or very irritated skin
- Temporary dryness or tightness, especially in high-foaming cleansers
- Redness or itching in those with a phosphate or surfactant sensitivity
- Eye irritation if the product accidentally gets into the eyes before rinsing
- Rare allergic contact dermatitis presenting as a rash or swelling
If any persistent discomfort, rash or swelling occurs stop using the product and consult a medical professional.
Comedogenic Rating
Rating: 1/5. Isotridecyl Phosphate is a lightweight, water-dispersible surfactant that rinses away instead of sitting on the skin. Its branched structure keeps it from packing tightly inside pores, which further limits clogging. Because of this low score, most people prone to acne or breakouts can use products containing this ingredient without extra worry. Only in very rich leave-on formulas could there be a slight chance of congestion, and even then it is minimal.
No widely published studies link this phosphate ester to comedones, and practical feedback from cleansers and micellar waters backs up its low-clog profile.
Summary
Isotridecyl Phosphate serves mainly as a gentle cleanser and an emulsifier. Its molecule has a water-loving head and an oil-loving tail, so it can lift away grime while helping water and oil mix smoothly. This dual action keeps textures even and leaves skin feeling clean yet comfortable.
It is not a headline-grabbing ingredient, yet formulators rely on it in everyday cleansers, shampoos and lightweight lotions because it quietly does its job without fuss. Safety data show it is well tolerated for most users, with only mild, short-lived irritation possible in sensitive situations. As with any new product, doing a quick patch test on a small area is a smart habit to make sure your skin agrees with the formula.