A fungal infection, typically affecting the scalp, can directly lead to hair loss. This condition is caused by fungi that invade the hair structure itself. The resulting hair loss often appears as distinct, localized patches rather than the generalized thinning seen in other common forms of alopecia.
The Primary Fungal Culprit
The main condition responsible for fungal-induced hair loss is Tinea Capitis, the medical term for ringworm of the scalp. This infection is caused by dermatophytes, a specific type of fungus that feeds on keratin, the protein that makes up hair, skin, and nails. Dermatophytes are classified into genera such as Microsporum and Trichophyton, with specific species varying by geographic region.
Tinea Capitis is highly contagious and is most commonly seen in preadolescent children. Transmission frequently occurs through direct contact with an infected person or animal, or indirectly through shared objects like combs, hats, or towels. Although children are the primary group affected, the infection can also occur in adults, particularly those who are immunocompromised.
Recognizing the Signs of Infection
Fungal hair loss presents with distinct visual characteristics. The most common presentation involves patches of hair loss on the scalp that are often accompanied by scaling resembling severe dandruff. These patches are typically round or oval and may show subtle redness or inflammation.
One distinct sign is the “black dot” pattern, where the hair shaft breaks off precisely at the scalp surface, leaving tiny dark remnants. Another variant, known as “gray patch” ringworm, involves hairs breaking off slightly above the scalp, leaving short, dull stubs. In some cases, the infection can trigger a severe inflammatory reaction known as a kerion, which manifests as a painful, pus-filled swelling that can lead to permanent scarring and hair loss.
The Mechanism of Hair Destruction
Hair loss results directly from dermatophyte fungi invading and structurally compromising the hair shaft. These fungi produce digestive enzymes, specifically keratinases, which break down the keratin protein within the hair. This enzymatic degradation weakens the hair, making it brittle and prone to breaking off easily near the scalp.
The invasion process is categorized based on where the fungal spores, called arthroconidia, form around or within the hair shaft.
Endothrix Infection
An endothrix infection, often caused by Trichophyton species, is characterized by the spores forming entirely inside the hair shaft, leaving the outer protective layer, the cuticle, intact.
Ectothrix Infection
In contrast, an ectothrix infection, often caused by Microsporum species, involves the spores forming a sheath around the outside of the hair shaft. This external formation causes destruction of the cuticle. Both invasion patterns result in the physical degradation and fracture of the hair.
Diagnosis and Medical Treatment
Tinea Capitis is suspected based on a visual examination and the characteristic appearance of hair loss and scaling. To confirm the diagnosis, a physician typically performs a potassium hydroxide (KOH) preparation. A sample of plucked hairs or scalp scale is mixed with KOH solution and examined under a microscope, allowing for the direct visualization of fungal elements, such as hyphae and spores.
Another diagnostic tool is the Wood’s lamp, which emits ultraviolet light. Some fungal species, such as Microsporum canis, will cause infected hairs to fluoresce a bright greenish-yellow color, though many common types do not. Definitive confirmation is often achieved through a fungal culture, where the collected sample is placed on a special medium to allow the specific fungus to grow and be identified.
Treatment for Tinea Capitis requires oral antifungal medication because the fungi live deep within the hair follicle and shaft, where topical creams cannot penetrate effectively. Griseofulvin is the primary medication, with alternatives including Terbinafine, Itraconazole, or Fluconazole. The course of treatment typically lasts several weeks to ensure the infection is completely eliminated.
Medicated shampoos containing ingredients like selenium sulfide or ketoconazole are often prescribed alongside oral medication. These shampoos help reduce the shedding of fungal spores from the scalp, minimizing the risk of spreading the infection. Following the full treatment course is necessary to prevent recurrence and ensure the hair follicles can recover and begin healthy hair regrowth.