Mascara is a popular cosmetic product used daily to enhance the eyes. Because it is applied close to a sensitive organ, its safety and shelf life are topics of concern. Old mascara can cause eye irritation, primarily due to the risk of microbial contamination. Understanding the mechanism behind this contamination and the potential health consequences is important for maintaining eye health.
The Primary Culprit: Bacterial Contamination
The tube and wand system creates an environment uniquely susceptible to microbial growth once the product is opened. Every time the wand is used, it picks up microorganisms present on the eyelashes and eyelid margin. The applicator deposits these bacteria directly into the dark, moist, and nutrient-rich formulation inside the tube.
This environment is ideal for proliferation, turning the mascara into a microbial incubator. Cosmetic formulas contain preservatives intended to inhibit this growth, but their effectiveness breaks down over time. As the preservative system weakens, bacteria multiply rapidly.
Common contaminants include species of Staphylococcus and Streptococcus, often found on human skin. Pathogenic organisms like Pseudomonas aeruginosa and Staphylococcus aureus have also been isolated in contaminated samples. Over time, these microorganisms can form a dense community, sometimes called a biofilm, on the inner surfaces of the tube and the wand. Re-application of this contaminated product introduces high concentrations of infectious agents to the eye surface, leading to irritation and infection.
Specific Eye Conditions Caused by Contamination
Using contaminated mascara can lead to a range of eye health issues, from mild irritation to serious infections. A common outcome is bacterial conjunctivitis, often referred to as pink eye, which results in inflammation of the conjunctiva. Symptoms include redness, discharge, and a gritty feeling in the eye. This infection is easily spread and requires immediate cessation of eye product use.
Contamination can also trigger localized infections along the eyelid, such as styes or blepharitis. A stye is a tender, red bump that forms when bacteria block an oil gland near the base of an eyelash. Blepharitis, an inflammation of the eyelid margins, is caused by bacterial buildup that results in redness, swelling, and crusty debris on the lashes.
Beyond bacterial infections, old mascara can physically damage the eye. As the formula ages, it can dry out and become flaky, and these dried particles may fall into the eye. These rigid flakes can cause superficial scratches or abrasions on the cornea, the transparent outer layer of the eye. A corneal scratch, or keratitis, is a serious condition that allows any present bacteria to enter the deeper layers of the eye, potentially leading to painful and vision-threatening infections.
Determining When Mascara Must Be Discarded
To minimize the risk of irritation and infection, experts recommend replacing mascara every three months after opening. This timeline is based on the rapid increase in microbial contamination that occurs once the preservative system begins to fail. The three-month rule holds regardless of how often the product is used, as contamination begins with the very first application.
Clear sensory warning signs indicate immediate disposal is necessary, even if the three-month mark has not been reached. These signs include:
- A noticeable change in the product’s smell, such as a sour or chemical odor, suggesting bacterial growth
- A shift in the mascara’s texture, such as becoming clumpy, dry, or stringy, signaling degradation
- Any redness, burning, or swelling after application, requiring immediate discontinuation of use