What Is Polyethylene Isoterephthalate?
Polyethylene Isoterephthalate is a man-made polymer created by joining units of ethylene glycol with terephthalic and isophthalic acids. The technical name, Poly(oxyethyleneoxy-1,4-phthaloyl, oxyethyleneoxy-1,3-phthaloyl), reflects these repeating building blocks. Because it is produced entirely in the lab, it is considered a synthetic ingredient rather than one sourced from plants or animals.
The material first appeared in industrial plastics during the late 20th century when manufacturers were looking for lightweight fillers with a smooth feel. Its stable structure, low cost and ease of production soon caught the attention of cosmetic chemists who adapted it as a safe way to add bulk and texture to powders and creams.
To make Polyethylene Isoterephthalate, chemists heat the raw acids with ethylene glycol in the presence of a catalyst. Water is removed, allowing the small molecules to connect into long chains. The resulting resin is cooled, ground into a fine powder and purified before it heads to cosmetic labs.
In beauty products you will most often see this ingredient in pressed powders, loose setting powders, blush, bronzer, facial masks that need extra body, stick foundations and some skin care creams where it helps create a rich cushioning feel.
Polyethylene Isoterephthalate’s Cosmetic Benefits/Uses
This ingredient plays one key role in formulas that rely on a pleasant texture and consistent payoff.
As a bulking agent, Polyethylene Isoterephthalate increases the volume of a product without affecting its active properties. It helps powders spread evenly, prevents clumping and gives creams a thicker, more luxurious feel. By occupying space it also allows manufacturers to achieve a desired package size and user experience while keeping the final cost reasonable.
Who Can Use Polyethylene Isoterephthalate
Polyethylene Isoterephthalate is considered gentle and non-reactive, making it suitable for most skin types including dry, oily, combination and normal skin. Sensitive skin generally tolerates it well because the particles are inert and do not penetrate deeply. Individuals with very acne-prone skin may wish to monitor use, as any added powdery filler can sometimes sit in pores and contribute to congestion if cleansing is inadequate, though this is uncommon.
The ingredient is fully synthetic and contains no animal-derived components, so products that rely on it are normally acceptable for both vegans and vegetarians. As always, check the complete ingredient list to ensure the rest of the formula aligns with personal ethics.
No data suggest that Polyethylene Isoterephthalate poses a specific risk to women who are pregnant or breastfeeding when used topically. This information is not medical advice and expectant or nursing mothers should consult their healthcare provider before introducing any new cosmetic product to be safe.
The polymer does not increase photosensitivity, so it will not make skin more prone to sunburn. Users should still follow standard sun protection practices appropriate for their skin and environment.
Potential Side Effects/Adverse Reactions
Reactions to topical Polyethylene Isoterephthalate can vary from person to person. The following list outlines potential side effects, but they are rare when the ingredient is included at approved levels in well-formulated products and most users will not experience them.
- Mild skin irritation such as redness or itching
- Clogged pores or breakouts in individuals prone to acne if the product is not thoroughly removed
- Eye irritation or watering if loose powder becomes airborne and contacts the eyes
- Respiratory discomfort if fine powder is inhaled in large amounts during application
- Allergic contact dermatitis in the very small number of people with a specific sensitivity to the polymer or accompanying formulation ingredients
If any unwanted reaction occurs discontinue use and consult a healthcare professional or dermatologist for guidance.
Comedogenic Rating
Rating: 1/5
Polyethylene Isoterephthalate is an inert plastic powder that stays on the skin’s surface and does not dissolve in oil. Because it does not melt into pores or feed surface bacteria it has a very low tendency to clog. The only time issues arise is when heavy layers of powder are left on oily skin without proper cleansing which can mix with sebum and create buildup.
Suitable for acne-prone and breakout-prone skin in most cases.
If you use dense powder products daily make sure to remove them fully at night so no residue remains that could trap oil or debris.
Summary
Polyethylene Isoterephthalate is mainly a bulking agent that adds volume and a smooth feel to powders and creams. Its lightweight plastic particles fill space so products spread evenly and feel cushiony without changing the performance of active ingredients.
The ingredient is not especially trendy but it shows up often in pressed powders, loose setting powders and some stick foundations because it is reliable, inexpensive and easy to work with.
Current research and decades of use show it is safe for topical application with only rare irritation reports. As with any new product it is smart to patch test first to be sure your skin gets along with the full formula.