Best Before vs Period After Opening... What does it all mean?

Best Before End vs. Period After Opening: What Do These Cosmetic Expiry Marks Really Mean?

When I started my new venture into skincare, I was very suprised to learn more about what all of the symbols actually mean. I feel this is so important to understand, so I wanted to share it with you. This is not only important for skincare, but especially makeup, ie Mascara and eyeshadows. I do not keep any makeup past 6 months of opening.

When you pick up a skincare or makeup product, you’ll often find two types of expiry-related symbols: Best Before End (BBE) dates and Period After Opening (PAO) icons. They look simple—but understanding the difference between them is essential for keeping your skin healthy, your products effective, and your routine free from mouldy surprises. (FYI - I decided to choose PAO for my product of 6 months as technically I have already opened the oil once when making it and also keep the product at its best. As the BMB Beauty balm contains no water, the oils and butters will stay much fresher for longer and prevent risk of product going off....

Let’s break them down.

What Is “Best Before End”?

The Best Before End (BBE) date is usually printed as “EXP”, “Use by”, or a small hourglass symbol, followed by a month and year.It indicates how long the product will remain stable and safe before it is opened—assuming it’s been stored correctly.

Key points about BBE:

• Applies to unopened products.

• Often used when a product has a shelf life of less than 12 months.

• After the BBE date, the formula may begin to degrade in ways you can’t always see or smell.

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Why BBE matters:

Ingredients—especially natural extracts, SPF filters, and preservatives—can slowly break down over time. Using expired, unopened cosmetics may lead to:

• reduced effectiveness (e.g., sunscreen losing protection)

• textural changes (separation, clumping, odd smell)

• increased risk of irritation if the formulation becomes unstable

What Is “Period After Opening (PAO)”?

The PAO symbol looks like a tiny open jar with a number on it—6M, 12M, 24M, etc.This tells you how long the product stays safe and effective after you’ve opened it.

Key points about PAO:

• The countdown starts the moment the seal is broken.

• It reflects how long the preservative system can protect the formula once it’s exposed to air, light, and bacteria from fingers or applicators.

• PAO varies depending on the product type—mascara may be 6M, while face creams might be 12M.

  
  

Why PAO matters:

Once opened, cosmetics become more vulnerable to:

• microbial contamination

• oxidation (when air breaks down ingredients)

• changes in texture, smell, or performance

• mould growth, especially in products with water content

Why Following These Dates Helps Prevent Skin Irritation

Expired or poorly preserved cosmetics can irritate your skin even if they look normal. Here’s why:

1. Ingredient Breakdown

Over time, active ingredients can oxidize or chemically degrade.This can cause:

• redness

• burning

• sensitivity

• breakouts

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For example, old vitamin C serums can oxidise and become irritating.

2. Bacterial Growth

Every time you touch a product with your fingers or use a wand near your eye, bacteria get introduced.If the preservatives stop working (which happens after the PAO), bacteria can multiply rapidly.

This can lead to:

• rashes

• clogged pores

• styes

• eye infections

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3. Mould and Fungal Growth

Moist, nutrient-rich creams are perfect environments for mold and yeast—especially once the product is older.Even if you can’t see the growth yet, spores can be present and harmful.

How to Keep Your Products Safe and Fresh

• Mark the opening date with a small sticker or marker.

• Close lids tightly to limit air exposure.

• Avoid dipping fingers directly into jars—use a clean spatula if possible.

• Store in a cool, dry area, away from direct sunlight.

• Replace high-risk products (like mascara and liquid eyeliner) more frequently.

  
  

The Bottom Line

Best Before End tells you how long a product stays good unopened. Period After Opening tells you how long it stays safe once you use it.

Both exist to protect your skin—and ignoring them can lead to irritation, ineffective products, and even mould or bacterial contamination. By understanding these symbols, you can keep your skincare routine safe, fresh, and performing at its best.

The BMB beauty balm contains is a pure waterless product with zero added fragrance or chemicals to keep your skin fully hydrated and free from harmful toxins. ( Use dry, clean hands or a spatual to apply to products, and remember to keep in a cool, dry place for maximum freshness.