What Expiration Symbols Actually Mean
Most makeup products carry two types of date information: a best before date (sometimes stamped on the bottom of packaging) and a Period After Opening symbol, commonly called the PAO. The PAO looks like a small open jar with a number inside — "12M" means the product is formulated to remain stable and safe for 12 months after you first open it.
These aren't arbitrary marketing devices. Cosmetic chemists set PAO windows based on how long a formula's preservatives can effectively control microbial growth. Once that window closes, preservative efficacy can decline — not dramatically overnight, but meaningfully over time. For products used near the eyes or on broken skin, that matters more than it might for, say, an eyeshadow palette stored in a dry environment.
Unopened products stored in cool, dry conditions often remain stable beyond their printed date, but once you've introduced air, fingers, or water into a formula, the clock is running. If you can't find a PAO on a product, a general rule used in the industry is: discard water-based formulas (foundations, liquid blush) within 12 months of opening and anhydrous (oil- or wax-based) formulas like lipstick within 18–24 months.
When Smell and Texture Are Your Guide
Even within a PAO window, a product can degrade if stored in a hot, humid environment (like a bathroom shelf). If a formula smells rancid, has separated in a way that won't re-blend, or has noticeably changed in texture or color, treat that as a signal to discard it regardless of the date. Your senses are often a reliable early-warning system.
Which Products Carry the Highest Risk
Not all makeup ages the same way. Mascara and liquid eyeliner are consistently flagged by dermatologists and ophthalmologists as the highest-risk products because the applicator is repeatedly introduced into the tube, creating warm, moist conditions where bacteria — including strains that can cause eye infections — can multiply. The standard guidance is to replace these every two to three months, regardless of how much product remains.
Liquid and cream foundations and concealers are next in line. Because they contain water and are often applied with fingers or sponges, they're more vulnerable to contamination than powders. If you're working with a pump dispenser, you're in better shape than dipping fingers directly into a jar — the latter introduces bacteria at every use. For sensitive or acne-prone skin, this distinction is worth paying attention to. Our guide on makeup habits for sensitive skin explores how application methods factor into irritation risk.
Powder products — blush, bronzer, eyeshadow — are more forgiving because they lack the water activity that supports microbial growth. However, they can still harbor oils and bacteria from brushes and fingers over time. Compact powders that are visibly discolored, cracked, or have a slick film on the surface should be discarded.
2–3 months
Recommended mascara replacement interval
Eye care professionals and cosmetic safety guidance consistently cite this window to reduce infection risk from mascara tube contamination.
12 months
Typical PAO for liquid foundations
Most water-based liquid formulas are formulated with preservative systems designed to remain effective for up to 12 months after first opening.
Brush and Tool Hygiene: The Overlooked Piece
A product can be perfectly fresh, but if the brush applying it hasn't been cleaned in weeks, you're transferring accumulated oils, dead skin cells, and bacteria directly onto your face at every use. This is one of the more common — and correctable — contributors to persistent breakouts and skin irritation.
Wash makeup brushes at least once a week with a gentle cleanser.
Brushes used daily on skin pick up oil, bacteria, and product buildup quickly. Weekly washing reduces the bacterial load transferred to your face and prevents buildup that can clog pores over time.
Avoid double-dipping applicators into product jars with bare fingers.
Each time an unwashed finger enters a jar, it introduces bacteria and skin debris into the formula. Over weeks, this shortens the effective lifespan of the product and increases contamination risk.
Discard mascara and liquid eyeliner every two to three months.
The warm, enclosed environment inside mascara tubes is particularly hospitable to bacterial growth. Because these products are used near the eyes, the risk of infection from contaminated formulas is higher than with other product types.
Store products away from humidity and direct heat.
Heat and humidity accelerate formula breakdown and compromise preservative systems even within a product's stated PAO. Bathroom shelves are common storage spots but are often the worst environment for preserving makeup.
Sanitize hard-surface tools and palette surfaces regularly.
Metal eyelash curlers, tweezers, and eyeshadow palettes accumulate oils and residue that aren't obvious to the eye but can contribute to skin and eye irritation over time.
If you're also refining your overall skincare approach, a skincare routine audit can help you identify whether products or tools might be behind ongoing skin concerns.
Quick Actions to Lower Your Risk Today
You don't need to overhaul your entire collection at once. A few targeted habits create meaningful improvement in makeup hygiene without a lot of time or expense.
If you're streamlining your collection, a minimalist makeup routine naturally reduces hygiene complexity — fewer products to track, fewer tools to clean. And when choosing new foundations or concealers, understanding how formulas are constructed helps; see our guide on foundation coverage and finish for context.
This article is for general informational and educational purposes only. It is not a substitute for professional medical or dermatological advice. If you are experiencing persistent skin irritation, eye infections, or other skin concerns, consult a qualified healthcare professional.
