Types of collagen: what types I, II, and III do and where each is found

If you are reading supplement labels, it is best to separate biology from marketing. In the European Union, health claims may only be used if they are authorized and included in the EU register, and food labelling cannot attribute the ability to prevent, treat, or cure diseases to a food. (food.ec.europa.eu)

In this article, you will see what each type of collagen does, where it is found, and how to interpret it rigorously. If you want to expand your focus on the skin afterwards, you can save this guide on facial collagen and how to stimulate it safely.

What collagen is and why it is important to distinguish its types

Collagen is an essential structural protein in connective tissues. A general review published in 2024 reminds us that there are at least 28 types, although types I, II, III, and IV are the most common in biomedical practice. The key lies not only in the name, but in the tissue where they appear and in the architecture they help to build.

When we talk about collagen, we are talking about mechanical support, the organization of the extracellular matrix, and different properties depending on the tissue. That is why it makes no sense to lump together collagen from the dermis, cartilage, and a more flexible reticular network. (scielo.br)

Quick summary of types I, II, and III

Type	Main function	Where it is found	Quick idea
Type I	Provides mechanical strength and structural support.	Dermis, tendons, ligaments, bone, and dentin.	It is the most abundant collagen and best represents the idea of tissue firmness.
Type II	Forms the basis of the cartilage matrix and is important for normal joint function. (ncbi.nlm.nih.gov)	Cartilage, vitreous humor, and inner ear.	It is the key collagen of hyaline cartilage.
Type III	Forms reticular fibers and accompanies type I in soft tissues. (pmc.ncbi.nlm.nih.gov)	Skin, blood vessels, and intestine.	It creates a more flexible network, very common alongside type I in the dermis.

The useful idea is simple: type I provides firmness, type II organizes cartilage, and type III builds a more flexible mesh, especially in the skin and blood vessels.

What each type of collagen does

Type I, the most abundant and the one that provides the most strength

A 2021 review on type I collagen describes it as the most abundant type and highlights its presence in the skin, tendons, ligaments, bone, and other tissues with high mechanical demands. In simple terms, it is the one most associated with strength, support, and tissue architecture. (pubmed.ncbi.nlm.nih.gov)

In the dermis, type I does not work alone, but it does play a central role in tissue firmness. That is one of the reasons it usually appears when explaining skin aging from a structural perspective, although that does not mean that a supplement will automatically translate into a clinical promise.

Type II, the main one in cartilage

The 2024 update of GeneReviews highlights that type II is an essential component of the cartilage extracellular matrix and that it is important for normal joint function. It also participates in the development and function of the eye and inner ear. That is why it appears mainly in cartilage, vitreous humor, and related structures.

The important thing here is not to confuse structural function with a promise of results. The fact that type II is key in cartilage does not mean that any product mentioning it is authorized to promise concrete benefits for the joints. In the EU, health claims are only valid if they are authorized and included in the official register.

Type III, the flexible network that accompanies type I

Type III forms reticular fibers and appears prominently in the skin and blood vessels. Reviews focused on its distribution also describe it as an essential component of internal organs such as the intestine and uterus, in addition to its presence in tissues where flexibility is as important as strength. (pmc.ncbi.nlm.nih.gov)

In the skin, type III usually coexists with type I. This coexistence explains why it makes no sense to talk about a single skin collagen, because the dermis functions as a network where both types complement each other. If you are interested in that more visual approach, you can also read about flabby skin on the face and body with LED light.

How they combine in tissues

They do not act in isolation. In the skin, types I and III share the architecture of the dermis, while in cartilage, type II is associated with other collagens to organize a stable matrix. That combination explains why different tissues need different proportions of collagen.

In other words, collagen is a family of support proteins, not a single ingredient with the same role everywhere. Understanding that difference helps to better read popular information and also to interpret with more judgment what appears on a package.

What can be legally said about collagen in foods and supplements

In the European Union, health claims must be authorized and appear in the EU register. In addition, labelling cannot attribute to a food the ability to prevent, treat, or cure human diseases. That is why, when talking about collagen as an ingredient, it is best to read any commercial message with great caution.

The authorized claim related to this topic is that of vitamin C: it contributes to the normal formation of collagen for the normal function of the skin, cartilage, gums, teeth, and blood vessels. That claim belongs to vitamin C, not to collagen as an automatic product promise. (eur-lex.europa.eu)

How to read a supplement label with judgment

• Check the source and declared type, because hydrolyzed collagens are mixtures of amino acids and peptides whose profile depends on the raw material and the hydrolysis method. (pmc.ncbi.nlm.nih.gov)
• Look for a transparent label regarding allergens, batch, and composition, and be wary of messages that sound like disease prevention or treatment, because that class of messages is not allowed for foods. (aesan.gob.es)
• If you are pregnant, breastfeeding, under 18, or have kidney, liver, or heart disease, or are following a treatment, consult a doctor or pharmacist first. (aesan.gob.es)
• In Spain, food supplements are notified and registered according to specific regulations, within the European food regulatory framework. (aesan.gob.es)

If you want to continue with a popular reading on skin and collagen, you can expand later with facial phototherapy in 2026, a guide that places light technology in the context of skin care.

Frequently asked questions

What precise role do types I, II, and III collagens play in the body, and how do they interact with each other?

Type I provides strength and support in tissues such as skin, tendons, ligaments, and bone. Type II organizes the cartilage matrix and is key to its normal structural function. Type III forms a more flexible network, common in skin and blood vessels, and usually coexists with type I. They do not act in isolation, but as part of an extracellular matrix that changes according to the tissue and its mechanical needs.

Where are type I, type II, and type III collagens mainly found in the human body?

Type I appears mainly in the dermis, tendons, ligaments, bone, and dentin. Type II is concentrated in cartilage, vitreous humor, and the inner ear. Type III is very present in the skin, blood vessels, and intestine. That distribution is not decorative, but functional: each type specializes in a class of tissue and a different architecture of the extracellular matrix.

Is type II collagen specific to cartilage, and what concrete contributions does it have for the joints?

No, it is not exclusive to cartilage, because it also appears in the eye and inner ear. Its main biological role is structural, since it is an essential component of the cartilage matrix and normal joint function. Now, that biological reality should not translate into an automatic commercial promise. In the EU, health claims must be authorized and registered, and they cannot imply that a food treats a disease.

How to differentiate the effects of type I collagen and type III collagen on the skin and connective tissues?

Type I is associated with strength and support, that is why it dominates in the dermis, tendons, ligaments, and bone. Type III accompanies type I in the skin and blood vessels, with a more flexible and reticular network. The important difference is not fashion, but structure: both collaborate in the dermis, but they do not perform exactly the same mechanical function. Thinking of only one as “the skin collagen” oversimplifies reality.

What foods or supplements contain mostly type I, II, or III collagen, and how to choose them well?

Foods are not usually labeled as type I, II, or III. In practice, the raw material comes from animal tissues rich in collagen, and in supplements it is usual to find hydrolyzed collagen or gelatin, that is, mixtures of peptides and amino acids whose profile depends on the source and the process. To choose with judgment, look at the origin, the declared form, the allergens, and the absence of therapeutic promises. If you are pregnant, breastfeeding, under 18, or have a disease, consult a professional first.

And now what?

If you want to continue deepening into skin care from a clear and practical approach, visit Kumo Balance and continue later with facial rejuvenation at home with LED technology.