Hair follicles
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Hair follicles (folliculi pili) are specialized anatomical structures of the skin responsible for the production and cyclical growth of hair. They constitute a complex mini-organ that includes not only the hair bulb but also epithelial sheaths, the dermal papilla, the sebaceous gland, and the arrector pili muscle attachment. Each hair follicle operates within a dynamic biological cycle, comprising the growth phase (anagen), regression phase (catagen), and resting phase (telogen). The proper structure and activity of hair follicles determine the density, thickness, and quality of hair. Disturbances in their function lead to various dermatological issues, including hair loss, inflammatory conditions, and scarring changes.
Hair follicles – what are they
A hair follicle is an indentation of the epidermis into the dermis, and in some locations, even into the subcutaneous tissue. Its structure is complex and includes:
- Hair bulb – the lower, expanded part of the follicle, containing the hair matrix (intensively proliferating cells).
- Dermal papilla – a connective tissue structure rich in blood vessels and growth factors (including VEGF, FGF), crucial for regulating the hair cycle.
- Inner and outer sheath – epithelial layers stabilizing the growing hair.
- Sebaceous gland – producing sebum, which protects the hair shaft and skin.
- Arrector pili muscle – responsible for the so-called "goosebumps."
The hair life cycle proceeds in stages:
- Anagen (growth phase) – lasts from 2 to 7 years on the scalp; about 85-90% of hairs are in this phase.
- Catagen (transitional phase) – a short involution phase (about 2-3 weeks).
- Telogen (resting phase) – lasts about 2-4 months; after it ends, the hair falls out, and the cycle starts again.
The activity of the hair follicle is regulated by hormonal (androgens, estrogens, thyroid hormones), immunological, and genetic factors. Dihydrotestosterone (DHT) holds particular significance in the pathophysiology of androgenetic alopecia, as it leads to hair follicle miniaturization and shortening of the anagen phase.
Hair follicles – diseases
Pathologies of hair follicles include both mild inflammatory conditions and chronic diseases leading to permanent hair loss. The most common ones are:
1. Folliculitis
- Etiology: bacterial (most commonly Staphylococcus aureus), fungal, or mechanical.
- Symptoms: pustules, erythema, tenderness at the follicle opening.
- Risk factors: shaving, depilation, excessive sweating.
2. Furuncle
- Deep follicular inflammation with tissue necrosis.
- Requires local or systemic treatment (antibiotic therapy).
3. Acne Vulgaris
- An inflammatory condition involving the pilosebaceous unit.
- Pathogenesis: overproduction of sebum, hyperkeratinization, colonization by Cutibacterium acnes, inflammatory response.
4. Cicatricial Alopecia
- An autoimmune or inflammatory process leading to follicle destruction and irreversible loss.
- Examples: lichen planopilaris, discoid lupus erythematosus.
Early diagnosis (dermatoscopy, trichoscopy, skin biopsy) is crucial in differentiating conditions and preventing permanent hair loss.
Hair follicles – hair loss
Hair loss (effluvium) is a symptom, not a disease entity. It may result from disturbances in the hair follicle cycle, its miniaturization, or inflammatory damage.
Most common causes:
- Androgenetic alopecia (AGA) – genetically determined, dependent on DHT.
- Telogen effluvium – sudden increase in the number of hairs in the telogen phase, often after:
- surgical stress,
- infections,
- childbirth,
- deficiencies in iron, zinc, vitamin D.
- Alopecia areata – an autoimmune disease.
- Hormonal disorders (thyroid, hyperprolactinemia).
- Medications (retinoids, cytostatics, anticoagulants).
Mechanisms leading to hair loss:
- Shortening of the anagen phase.
- Follicle miniaturization.
- Inhibition of matrix cell proliferation.
- Perifollicular fibrosis.
Therapeutic approach
Modern aesthetic medicine and dermatology offer methods to support hair follicle function:
- Microneedle mesotherapy of the scalp (nutrient cocktails, platelet-rich plasma).
- Autologous therapies (PRP, platelet-rich fibrin).
- Carboxytherapy of the scalp – improves microcirculation.
- Treatments using LED light and regenerative technologies.
- INDIBA® MED – radiofrequency therapy at 448 kHz supporting cellular metabolism and tissue blood supply.
In the case of androgenetic alopecia, the standard treatment remains topical preparations (minoxidil) and – in selected patients – systemic therapy (finasteride, dutasteride).
The effectiveness of therapy depends on:
- the duration of the problem,
- the activity of the hair follicle,
- the presence of inflammatory or scarring processes,
- individual genetic predisposition.
The earlier the treatment is implemented, the greater the chance of halting the process and improving hair density.
