≡ Menu

How are cosmetic products tested for safety?

They say that a magician never reveals the secrets of his or her tricks but I think that revealing the “tricks” of cosmetic chemists can help consumers by making them smarter. To that end, here’s an article written for cosmetic chemists on the topic of safety testing finished products.

Formulators of cosmetic products must ensure their products are safe for consumer use. The Food, Drug and Cosmetic Act of 1938 mandated quality and identity standards, prohibited false therapeutic claims, and clarified the FDA’s control of product cosmetic patch testadvertising, among other items. According to the Code of Federal Regulations (21 CFR 740.10a). Each cosmetic manufacturer is responsible for:

* using only safe and suitable ingredients
* substantiating the safety of those ingredients and of the finished product

FDA Cosmetic Regulation

This means that manufacturers of cosmetics in the United States, no matter how big or small, are obligated to perform safety tests on the products they produce. In fact, ingredients or finished goods whose safety has not been evaluated are misbranded (false, misleading, or fraudulent) and must have this text on the label:

“ Warning — the safety of this product has not been determined.”

The FDA can send warning letters, safety notices, and initiate recalls or withdrawals of product from the market. Safety testing is serious stuff!

Types of Safety Testing

The type of safety testing is often determined by area of contact (skin, eye area) and can be modified depending on the type of product and how it may be used e.g. diluted. Safety testing can also be used to generate product claims. Here are some examples:

* mildness
* hypoallergenic
* dermatologist tested

There are two commonly accepted methods for making skin safety assessments in the industry. These are the 21-Day Cumulative Irritation Test (CIT) and the Human Repeat Insult Patch Test (HRIPT). Both of these methods use a trained observer to measure inflammation, which is the body’s general response to distress. The four classic signs of inflammation are:

– Erythema (Redness)
– Edema (Swelling)
– Pain
– Heat

21-Day Cumulative Irritation Test

The CIT measures inflammatory response to an irritant. It occurs immediately and only at the site of exposure. The response tends to be universal (produces a reaction in most individuals) and depends on the strength and duration of exposure. In this type of test products are applied to human subjects under an occluded patch, usually on the back, and graded daily for a total of 21 days. A known irritant and a non-irritant are run as controls. The scores are summed across all subjects to provide a cumulative irritation score. The score can be compared to the large pool of historical test data to make judgments about irritation potential. An additional challenge phase can be run two weeks after the last patch was removed to understand potential for sensitization, which is usually measured with the HRIPT.

Human Repeat Insult Patch Test — Sensitization, Allergic Response

Sensitization is the process by which a person becomes, over time, increasingly allergic to a substance through repeated exposure to that substance. It is very different from irritation because it involves immune response, the reaction becomes worse with repeated exposure, and it is usually specific to individuals. The HRIPT consists of 2 phases, possibly 3.

Phase I is the Induction Phase where product is applied to the skin a few times during the course of a week. This is a followed by a two-week rest period after which the skin is exposed to the product again in Phase II or the Elicitation Phase. A response in Phase II is usually allergic in nature and Phase III is used to verify and better define the reaction.


The HRIPT method can also be modified for photosensitization, which is particularly useful for sunscreens. Photosensitization can occur when normally harmless molecules undergo changes when exposed to UV light.