How do I find the batch code on my cosmetic or skincare product?

The batch code is stamped, embossed, or dot-matrix printed directly onto the container during factory production. It is typically found on the bottom of bottles or jars, pressed into the top crimped edge of tubes, or printed near the barcode. Unlike barcodes (which only identify the general product SKU), batch codes are typically 3 to 6 alphanumeric characters (such as A34, 28X301, or 4B01) that identify the exact day and factory run.

How long does makeup last before it expires?

Unopened cosmetics stored in a cool, dry environment usually have an unsealed shelf life of 24 to 36 months. Once opened, look for the Period After Opening (PAO) jar symbol. As a general rule: mascaras and liquid eyeliners last 3 to 6 months; liquid foundations and concealers last 12 months; cream blushes and lip oils last 12 to 18 months; powder eyeshadows and blushes last 24 months; and traditional lipsticks last 24 to 36 months.

What does the Period After Opening (PAO) open jar symbol mean?

The PAO symbol is an icon of an open cosmetic jar with a number followed by the letter 'M' (e.g., 6M, 12M, 24M). This indicates the number of months the formulation remains safe, hygienic, and active after the protective safety seal has been broken.

Does the AI Makeup Look Auditor upload my photo to external servers?

No. The Mirha & Co. AI Makeup Auditor operates 100% locally on your device via client-side HTML5 Canvas computer vision. Your photo is never sent to external servers, cloud databases, or third-party AI APIs, guaranteeing complete personal privacy.

What is the correct everyday makeup application order for zero pilling?

To prevent pilling and rolling: 1) Allow sunscreen to set for 2 full minutes before makeup. 2) Spot conceal only inner eye corners and red spots rather than painting thick foundation across the entire face. 3) Dab cream blush high along the cheekbones. 4) Lightly dust translucent powder only on the nose wings, leaving cheeks radiant. 5) Finish with brushed brows and a hydrating lip tint.

How do I determine whether my skin undertone is Warm, Neutral, or Cool?

Examine the veins on the inside of your wrist in natural daylight. If your veins look greenish and gold jewelry flatters you best, you have a Warm (Golden) undertone. If your veins look blue or purplish and silver jewelry brightens your skin, you have a Cool (Rosy) undertone. If your veins are blue-green and both gold and silver look harmonious, you have a Neutral (Balanced) undertone.

Independent reviews. Honest opinions. Affiliate links disclosed.

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Search BrandActive: M·A·C Cosmetics

Stamped Batch CodeFormat: 3 chars (e.g. A34)

Quick tests:

Fresh & Safe to Use

4 months shelf life left

Manufactured

Mar 2024

Unopened Expiry

Mar 2027

Once Unsealed (PAO)

Mascara: 6m · Creams: 12m

Freshness Life11%

Clinical Beauty Knowledgebase

The Definitive Cosmetic Shelf Life & Batch Code Guide

Everything you need to know about factory lot codes, Period After Opening (PAO) safety, and how to preserve barrier health against oxidized formulas.

Period After Opening (PAO) Quick Reference

When should you actually discard opened cosmetics?

Even if a batch code indicates an unsealed factory shelf life of 36 months, the internal countdown begins the moment the protective seal is broken and oxygen, humidity, and fingertip microbes enter the container.

Product Category	Standard PAO	Degradation Warning Signs	Barrier Risk
Mascara & Liquid Liners	3 – 6 Months	Dry clumps, alcohol or gasoline odor	High (Corneal infection risk)
Liquid Foundation & Concealer	12 Months	Water-oil separation, sour smell, darker color	Moderate (Acne flare-ups)
Cream Blush & Lip Oils	12 – 18 Months	Sticky gummy texture, rancid oil odor	Moderate (Perioral dermatitis)
Powder Shadows & Blushes	24 Months	Hard film on surface, loss of color payoff	Low (Preserves well if kept dry)
Lipsticks & Wooden Lip Liners	24 – 36 Months	Wax sweating (beads on bullet), crayon odor	Low (Sharpening refreshes wood)

Estée Lauder Group

M·A·C, Clinique, Tom Ford, Bobbi Brown

Uses the industry-standard 3-character alphanumeric format. The first character represents the factory batch lot, the second is the month (1–9 for Jan–Sep, A–C for Oct–Dec), and the third digit is the year of production (e.g., A34 = March 2024).

L'Oréal Group

Maybelline, CeraVe, Kiehl's, YSL, Lancôme

Uses a 6-character factory code. The 3rd character represents the year of manufacture using sequential alphabet keys (T=2020, U=2021, V=2022, W=2023, X=2024, Y=2025), and the 4th character encodes the production month.

LVMH & Dior Group

Dior, Guerlain, Givenchy, Fenty Beauty

Uses a 4-character format. The first digit represents the year (e.g., 4 = 2024), and the second letter represents the month based on Dior's 12-letter cycle (A through M, omitting the letter I to avoid confusion with the number 1).

Frequently Asked Questions

Cosmetic Freshness, AI Look Audits & Everyday Routines

How do I find the batch code on my cosmetic bottle?

Look on the base of the bottle, jar, or the crimped seal of the tube. Unlike long 12-digit barcodes, batch codes are short (3 to 6 characters), often stamped in dot-matrix ink or debossed directly into the plastic or glass.

Does the AI Look Auditor store or upload my face?

No. Analysis runs completely on your local device CPU/GPU via HTML5 2D Canvas colorimetry. No images, selfies, or facial data ever touch external servers or cloud AI providers.

What makes everyday makeup pill or roll off?

Pilling happens when silicone-based products are layered over water-based products without allowing proper drying time. Always wait 2 full minutes after applying sunscreen before tapping on concealer or blush.

How do I prevent my foundation from looking ashy or grey?

Ashiness occurs when cool-toned (pink) foundations are applied to warm golden or olive undertones. Use our Seasonal Color Harmonizer to check your neck undertone match before purchasing.

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