The potential hazards of using expired cosmetics

The most immediate hazard of expired cosmetics is microbial contamination. Water-based products such as liquid foundation are very susceptible to bacterial growth [1], and according to Mayo Clinic Health System, liquid products used near the eye, such as mascara and liquid eyeliner, have an increased risk of spreading bacteria [2].

Common pathogens found in in-use cosmetics include:

• Staphylococcus aureus: Found in used lipsticks, eyeliners, mascaras and beauty blenders in an Aston University study [9]; it causes most staph infections, and skin infections are the most common kind [11].

• Pseudomonas aeruginosa: One of the two most common bacteria in used eye cosmetics in a 2023 review [3]; mascaras contaminated with it have been linked to corneal ulcers, especially when the applicator scratches the eye [10].

• Streptococcus: The most common bacterium in the used skin and eye cosmetics in the same review [3].

Using contaminated products can make your skin break out or become irritated, and can even introduce infections [4].

Even if a product remains free of bacteria, its chemical composition changes over time. Heat breaks down preservatives, and light and air oxidize pigments and active ingredients [5]. That is why a beige foundation kept too long can take on a slightly more orange color, and why a product that smells odd, or different from when you bought it, should be thrown out [2].

Contact Dermatitis and Chemical Burns

Changes in the chemical composition of expired makeup can result in Contact Dermatitis, characterized by red, itchy, or scaly patches on the skin [1]. In extremely rare cases, expired makeup may cause chemical burns [1].

Fewer preservatives does not mean a longer life: products with unconventional preservatives, or none, can have an unusually short one, so date them when you open them [5].

In the United States, no law requires cosmetics to carry an expiration date, though many products show one anyway [1]. Others carry the Period After Opening (PAO) symbol, an icon of an open jar with a number inside (e.g., 6M, 12M, 24M) [4].

For products with no date or open-jar symbol, Ohio State dermatologist Susan Massick and Mayo Clinic Health System give these general timelines [2] [4]:

Cosmetic chemistry is delicate. Preservatives, pigments, and active ingredients are designed to remain stable within narrow environmental parameters.

1. Temperature Control

Most makeup is best kept at a steady room temperature: a drawer that stays constant does more than a spot that swings between hot and cool [5].

• Heat Damage: Heat breaks down preservatives, makes emulsions separate and softens wax-based products, which is why lipstick fails first in heat. Keep makeup away from heaters, sunny walls and windows [5].

• Cold Damage: The fridge helps only some products: it slows spoilage in natural, preservative-free formulas and stops wax products melting in summer, but oils and butters can harden, and emulsions can separate when the temperature swings [5].

2. Light Protection

Light and air oxidize pigments and active ingredients: oxidation is what shifts a beige foundation toward orange, and vitamin C oxidizes readily in air and light. A closed drawer takes care of light and cuts down air exposure, and tight caps cover the rest [5].

3. Humidity and Moisture

The bathroom is often the worst place for storage. Bathroom moisture makes bacterial and fungal growth easier, and powders need to stay dry [5]. That is why experts advise keeping makeup in a cool, dry place away from moisture, such as a vanity kit or a drawer, and never in the bathroom [6].

Preventing infection starts with the environment in which you apply your makeup. Ophthalmologists and dermatologists give the same basic rules [4] [7]:

1. Wash Your Hands and Face

Before touching your eyelids, ensure your hands are scrubbed clean. Any bacteria on your fingers can easily transfer to the delicate mucous membranes of the eye. Similarly, make sure your face and eyelids are very clean before starting [4] [7].

2. Apply Outside the Lash Line

A common mistake is “tightlining” or applying eyeliner inside the lash line on the “waterline.” The American Academy of Ophthalmology advises always applying makeup outside the lash line, away from the eye, to avoid blocking the oil glands of the upper or lower eyelid (the Meibomian glands), whose oil protects the eye’s surface [7].

3. Never Share Cosmetics

Sharing eye makeup is equivalent to sharing germs. Pink eye (conjunctivitis) caused by viruses and bacteria is very contagious, and the CDC advises against sharing eye or face makeup and makeup brushes [8]. When testing products in a store, use only fresh applicators and samples no one else has used; the safest choice is to avoid store samples altogether [7].

The risks show up in laboratory tests, not only in anecdotes. Aston University researchers tested donated used lipsticks, lip glosses, eyeliners, mascaras and beauty blenders: 79 to 90% were contaminated with bacteria, including Staphylococcus aureus and E. coli; 93% of the beauty blenders had never been cleaned, and 64% had been dropped on the floor and used again [9]. Products with unconventional or no preservatives, such as some “natural” formulas, can have an unusually short life, so check their scent and texture [5].

1. Audit Your Stash: Go through your makeup bag today. Throw away any liquid eye products older than 3 months.
2. Label Your Products: Use a permanent marker to write the “Open Date” on the bottom of new foundations and creams.
3. Sanitize Tools: Wash makeup brushes every 7 to 10 days [2] and replace sponges every 3 months [1] to prevent cross-contamination.
4. Storage Matters: Move your makeup out of the humid bathroom. Cosmetics break down faster when exposed to heat and moisture [1].

Your skin is your largest organ. While discarding an expensive palette feels wasteful, the cost of treating a severe eye infection or chronic dermatitis far outweighs the price of a fresh replacement.