Your hair follicles have an immune system - and it does more than you might think

When we think about the immune system, we tend to think about protection. Fighting infections. Recognising danger. Keeping us well.

We probably don’t think about it helping a hair grow.

But around each hair follicle is a small community of immune cells. Some help defend it. Some help regulate its cycle. Others communicate with the stem cells involved in producing the next hair.

A review published in October 2026, Immune Cells in Hair Follicle Physiology and Pathology, explores this relationship. What interests me most is that the immune system can help sustain hair growth, yet also contribute to hair loss when those relationships become disrupted.

Here is what I took from it, and where the science still has questions to answer.

A hair follicle is a living, changing structure

The hair we can see is only part of the story. Beneath the skin, the follicle is a miniature organ that repeatedly moves through growth, regression and rest.

These phases are called anagen, catagen and telogen. Rather than growing continuously for ever, each follicle cycles between them.

Stem cells help maintain and regenerate the follicle as it moves into another growth phase. Their behaviour depends partly on messages from surrounding cells, including immune cells.

This means that finding immune cells around a follicle does not mean something is wrong. They belong there.

Some immune cells help hair follicles grow

The review describes several types of immune cell with different, sometimes overlapping roles.

Macrophages help clear cellular debris and coordinate tissue responses. Experimental studies suggest that some macrophage signals help activate follicle stem cells, while others help keep those cells resting. The effect depends on the cells’ state, their signals and the stage of the hair cycle.

Regulatory T cells, often shortened to Tregs, help restrain excessive immune responses. Research, particularly in mice, suggests that they also communicate with follicle stem cells and support the transition into growth. They appear to have a role in both protecting the follicle and helping it renew itself.

Mast cells are often associated with allergy, but their activities are much broader. They release chemical messengers and can influence inflammation and hair cycling. Their effects vary with the circumstances; they cannot simply be labelled harmful.

Other cells, including Langerhans cells, help with immune surveillance, while specialised groups of T cells contribute to tissue maintenance, repair or inflammation.

The useful idea here is balance. Healthy hair growth involves coordinated immune activity, rather than an absence of it.

What is hair follicle “immune privilege”?

Certain parts of the follicle have a degree of protection from potentially damaging immune reactions. This is called immune privilege.

It does not mean the follicle is disconnected from the immune system. It means that local signals help limit immune recognition and unnecessary attack in particular regions.

Think of it as a carefully maintained environment in which specialised cells can get on with their work.

That protection matters around the growing hair bulb and the region housing important follicle stem cells. When it breaks down, the consequences depend partly on which structures are affected.

Why this matters in alopecia areata

Alopecia areata is an autoimmune form of hair loss. Immune cells mistakenly target the follicles, interrupting normal hair production.

The review describes the important role of cytotoxic T cells: cells that normally help remove infected or abnormal cells. In alopecia areata, these cells participate in an inappropriate attack on the follicle, alongside a wider network of inflammatory signals.

Loss of immune privilege is an important part of this process.

Alopecia areata is classed as a non-scarring alopecia. Follicles can retain the capacity to produce hair, although regrowth is not guaranteed and the course varies considerably.

For me, this helps explain why understanding the biological process matters. A follicle whose growth has been interrupted presents a different problem from one that has been permanently destroyed.

Scarring hair loss involves a different kind of damage

The review also discusses conditions such as lichen planopilaris, discoid lupus erythematosus and folliculitis decalvans.

These conditions differ in their causes and immune activity, but can result in permanent follicle destruction and scarring.

One especially interesting detail is that macrophages associated with repair can also be associated with fibrosis - the formation of excessive scar tissue - in certain settings. Cells that support recovery in one context may contribute to damage in another.

This is another reason that “boosting” or “suppressing” the immune system is too broad an explanation for treating hair loss. Which process is involved, and where it is happening, matters.

How might stress affect this conversation?

The review explores connections between nerves, immune cells and the hair cycle.

In animal experiments, stress-related nerve signals can activate mast cells and alter macrophage behaviour. These changes can affect the follicle’s growth cycle.

This offers possible biological explanations for connections between stress and hair growth. However, much of the evidence discussed here comes from animal models. It does not establish that the same pathway explains an individual person’s shedding.

Nor does it mean that hair loss is someone’s fault, or that being told to relax is an adequate answer. Hair loss can itself be profoundly stressful.

Could we persuade the immune system to help hair grow?

This is the question that makes the research exciting. If some immune cells help wake resting follicle stem cells, could we learn to encourage those signals? If others help protect the follicle from attack, could we restore that protection when it fails?

Researchers are exploring these possibilities. Some experiments have even investigated how immune cells help new follicles form in wounded skin in animal models. That is a long way from growing new hair follicles on a human scalp, but it gives scientists something remarkable to investigate.

What stays with me is how much activity surrounds something we barely notice until it starts falling out. A hair grows because living cells beneath the skin cooperate: sending messages, responding to change, resting and starting again.

The immune system is part of that conversation. Learning its language could help us understand why hair stops growing - and how we might help it begin again.

Source: Dai C, Zeng F. Immune Cells in Hair Follicle Physiology and Pathology. Clinical, Cosmetic and Investigational Dermatology. 2026;19:594805. Published 20 October 2026. Read the paper.

This article explains a research review for general information. It does not replace an individual assessment or treatment advice.

Author: Dr Gwen Adey

First published: 01/11/26