Cosmetics can degrade in several ways. The FDA lists finger contact as a way to add bacteria and fungi, preservatives as substances that can break down over time, emulsions as products that can separate, and heat, sunlight, air, and temperature changes as causes of changes in color, texture, or smell. FDA shelf-life guidance

Microbial spoilage is one pathway, but not the only one. A product can also become unpleasant or unusable through oxidation, drying, phase separation, or package damage. FDA shelf-life guidance

What counts as a warning sign

An unusual or rancid smell, a major color change, new lumps or gritty texture, unexpected thinning or thickening, separation that does not remix as designed, a cracked container, or a broken seal are all good reasons to stop using a product and check the manufacturer’s guidance. These are practical caution signals, not a diagnosis of mold or a particular organism. FDA shelf-life guidance

The FDA also says warm or damp storage can make microorganisms grow faster and preservatives break down. Finger-dipping, sharing, or adding water can increase contamination risk. FDA microbiological safety guidance

What appearance cannot prove

“It looks fine” is not a microbial test. FDA manufacturing guidance calls for testing raw materials, water, finished products, and retained samples, including preservation adequacy under reasonably foreseeable storage and consumer use. Its microbiological methods manual describes enumeration and pathogen checks that cannot be replaced by looking at a jar. FDA GMP guidance FDA BAM Chapter 23 FDA BAM Chapter 23, July 2024 PDF

The reverse is true too: a separated product is not automatically contaminated. Emulsions can separate for physical reasons, and heat or freezing can alter texture without identifying a microbe. You still do not need to investigate it at home. A changed product is no longer a trustworthy product for your routine.

What about expiry dates?

For ordinary U.S. cosmetics, FDA says there is no law requiring a specific shelf life or expiration date on the label. Manufacturers remain responsible for determining how long a product stays safe and usable, and shelf life depends on product type, use, and storage. FDA shelf-life guidance

That means no printed date is not proof of indefinite safety. A printed date is also not permission to ignore a product that has changed or a package that was damaged. Eye-area cosmetics deserve extra caution because FDA notes their shorter practical shelf lives and the possibility of serious eye infections. FDA shelf-life guidance

Why appearance is not a test

Spoilage signs are asymmetric. A smell or texture change is enough reason to stop, but the absence of a smell or visible growth cannot certify that microbes are absent. Only appropriate manufacturing and laboratory controls can answer that question. FDA GMP guidance FDA BAM Chapter 23, July 2024 PDF

Evidence grade: strong, with product-specific uncertainty

The pathways and limits are well supported by FDA guidance. The uncertainty is the lifespan of any specific product without its stability, preservation, packaging, storage, and batch information. Follow the manufacturer’s storage instructions, avoid sharing or adding water, and discard a product that has changed rather than trying to rescue it.

Sources

Cosmetic safety information, not a laboratory diagnosis or a DIY preservation guide.