Trichomycosis Axillaris (trichomycosis palmellina, trichobacteriosis palmellina, trichomycosis nodosa, trichobacteriosis axillaris, Paxton’s disease)

Are You Confident of the Diagnosis?

What you should be alert for in the history

Trichomycosis axillaris is often asymptomatic. However, patients may report sweaty malodorous armpits, and some may be aware of nodules or concretions on the axillary hairs. Similar nodules may present on the pubic hairs (trichomycosis pubis). Discolored axillary sweat may stain clothing. A history of poor hygiene and axillary hyperhidrosis are frequently elicited.

Characteristic findings on physical examination

A rancid acid smell in the axillae may be first noted. Examination of the axillary hairs reveals yellow, red, or black, 1-2mm granular nodules or concretions surrounding hair shafts. This makes the hairs appear beaded. These nodules are firmly attached to the hair shaft and difficult to remove. The most common nodule color is yellow, although red and black are the most common colors in tropical climates (Figure 1).

Figure 1.

Trichomycosis axillaris.

There may be associated hyperhidrosis in the area, and sweat may be stained yellow, red, or black. There is no associated hair fragility or alopecia, and no underlying pigmentary change of the skin. Similar concretions may be seen on the pubic hair in a minority of cases (trichomycosis pubis). Other corynebacterial related conditions may also be seen on examination, including pitted keratolysis and erythrasma (the so-called corynebacterial triad).

Expected results of diagnostic studies

Trichomycosis axillaris is caused by several species of gram-positive Corynebacteria. A potassium hydroxide (KOH) preparation, followed by examination with light microscopy, will show the causative bacteria in the concretions. A culture is not necessary. A gram stain will also show slender purple rods under light microscopy. Wood’s light examination will show a dull yellow or gray-white fluorescence.

Diagnosis confirmation

The differential diagnosis of trichomycosis axillaris includes hair casts, piedra, pediculosis pubis, and artifacts from deodorants, creams, soaps, or powders. Microscopy and Wood’s light examination are useful to differentiate these conditions.

Hair casts are amorphous in appearance and do not show bacteria. They are easily mobile along the hair shaft.

White piedra is a fungal infection that can affect axillary hair. It appears as white, cream-colored, or brown nodules, which can easily be detached from the hair shaft. White piedra does not fluoresce. Furthermore, the KOH examination will reveal encapsulated arthroconidia or blastoconidia, and not bacteria.

Pediculosis pubis (pubic lice, crabs) involves the pubic area, but the axillary hairs can also be involved in some men. The nits, nymphs, and adult lice are identified with a magnifying glass and easily removed with forceps.

Who is at Risk for Developing this Disease?

Trichomycosis axillaris is a common condition worldwide. Approximately 25%-30% of adult males are affected. Women are less likely to be affected, in part because they commonly shave hair in the axilla. Axillary hyperhidrosis and poor hygiene are the most important risk factors. Warm climates and humidity are also risk factors.

What is the Cause of the Disease?

Trichomycosis axillaris is caused by several species of aerobic gram-positive Corynebacteria (mainly Corynebacterium tenuis) that colonize axillary hair shafts. It is not caused by a fungus, as the name originally implied. Moist areas rich in sweat glands, including the axillae (trichomycosis axillaris) as well as the pubic region (trichomycosis pubis) are favored sites for these bacteria.


Trichomycosis axillaris is a superficial bacterial infection of axillary hair. Corynebacteria produce a cement-like substance, which facilitates bacterial adherence to hair.

Electron microscopy shows destruction of the hair shaft cuticle, as well as superficial portions the hair cortex. The rancid odor is due to the ability of the Corynebacteria to metabolize testosterone and other hormones found in the apocrine sweat into several malodorous compounds. The different types of Corynebacteria produce different pigments, including yellow (trichomycosis axillaris flavus), red (trichomycosis axillaris rubra), and black (trichomycosis axillaris nigra).

Systemic Implications and Complications

Trichomycosis axillaris is a benign condition and not associated with systemic abnormalities; however, it is important to evaluate for Corynebacterial infections at other body sites, including the pubic area (trichomycosis pubis), feet (pitted keratolysis), and intertriginous areas (erythrasma). One study suggested that 13% of soldiers with pitted keratolysis had the full corynebacterial triad of trichomycosis axillaris, pitted keratolysis, and erythrasma.

Treatment Options

Treatment options are summarized in Table 1.

Table I.
Mechanical Shaving hairs in the affected area
Medical- topical – Benzoyl peroxide gels or washes
– Antibacterial soaps
– Topical clindamycin or erythromycin
– Prevention with antiperspirants or drying powders
Medical – systemic Oral erythromycin
Surgical None
Physical modalities None

Optimal Therapeutic Approach for this Disease

The most rapid and effective treatment is to shave hairs in the affected areas and prevent further recurrences with daily use of antibacterial soaps or benzoyl peroxide washes. Use of antiperspirants after bathing is important to reduce sweating. Antiperspirants with 20% aluminum chloride in anhydrous ethyl alcohol are particularly helpful because they reduce hyperhidrosis and are bactericidal.

Drying powders may also reduce moisture in the area. Attention to hygiene measures alone is usually sufficient to treat trichomycosis. Patients who do not wish to shave the axillary hair can still achieve clearance within a few weeks with daily washing with an antibacterial soap or benzoyl peroxide wash.

To promote more rapid resolution of the condition, a topicial antibiotic or benzoyl peroxide gel is frequently prescribed, in addition to the above hygiene measures. Twice daily use of topical 1% clindamycin lotion or 2% erythromycin lotion are effective and lead to clearance within 2 weeks. Benzoyl peroxide 5% gel or lotion is also effective, but may be irritating to some individuals and may bleach hair. Oral erythromycin at 250mg four times daily for 2 weeks can be prescribed if compliance is an issue.

The rancid odor may remain in clothing, and patients should be reminded to adequately wash or dry clean clothing.

Patient Management

Although treatment of trichomycosis axillaris is rapid and effective, preventive measures are essential to reduce recurrence. Use of antibacterial soaps, followed by use of an antiperspirant is recommended.

Unusual Clinical Scenarios to Consider in Patient Management

Any evaluation of chromhidrosis mandates an evaluation of the axillary (or pubic) hair for trichomycosis axillaris (or pubis).

What is the Evidence?

Bargman, H. “Trichomycosis of the scrotal hair”. Arch Dermatol. vol. 120. 1984. pp. 299(This was one of the first reports of trichomycosis involving the scrotal hair. Bargman described a 21-year-old male with trichomycosis of the axillary and pubic hair who responded completely following a 2-week twice-daily course of 1% clindamycin lotion.)

Crissey, JT, Rebell, GC, Laskas, JJ. “Studies on the causative organism of trichomycosis axillaris”. J Inv Dermatol. vol. 19. 1952. pp. 189-97. (The was the first report to outline the bacteria origin of trichomycosis axillaris. The authors believed that trichomycosis axillaris was due to a single strain of Corynebacteria, which they cultured and named Corynebacterium tenuis. The bacteria was cultured from each of twenty-eight patients with trichomycosis axillaris. The authors estimated an incidence of the condition of 23%, after examining 100 consecutive patients in the United States.)

Freeman, RG, McBride, ME, Knox, JM. “Pathogenesis of trichomycosis axillaris”. Arch Dermatol. vol. 100. 1969. pp. 90-5. (Seven patients with trichomycosis axillaris were studied. In six of the seven cases, three species of Corynebacterium tenuis were isolated. The diptheroids producing red granules were similar to those producing yellow.)

Orfanos, CE, Schloesser, E, Mahrle, G. “Hair destroying growth of corynebacterium tenuis in the so-called trichomycosis axillaris”. New findings from scanning electron microscopy. Arch Derm. vol. 103. 1971. pp. 632-9. (The authors showed that trichomycosis axillaris is due to extensive bacterial colonization of hair, causing destruction of the cuticle as well as the superficial hair cortex.)

Paxton, FV. “On a disease condition of the hairs of the axilla, probably of parastic origin”. J Cutan Med. vol. 3. 1869. pp. 133(Paxton provided the first description of trichomycosis axillaris. Thereafter, the disease was frequently referred to as Paxton’s disease.)

Rho, NK, Kim, BJ. “A corynebacterial triad: prevalence of erythrasma and trichomycosis axillaris in soldiers with pitted keratolysis”. J Am Acad Dermatol. vol. 58. 2008. pp. S57-8. (This was a prospective study, evaluating the prevalence of trichomycosis axillaris and erythrasma in Korean soldiers presenting with pitted keratolysis. Fourteen of 108 patients (13%) had the full triad of pitted keratolysis, erythrasma, and trichomycosis axillaris. Twenty-two patients (20.4%) had trichomycosis axillaris and pitted keratolysis. This study supports the notion that these three corynebacterial infections may frequently coexist.)

Savin, JA, Somerville, DA, Noble, WC. “The bacterial flora of trichomycosis axillaris”. J Med Microbiol. vol. 3. 1970. pp. 352-6. (The authors showed that trichomycosis was due to at least three distinct isolates of Corynebacteria. In a group of institutionalized patients studied in England, 230 of 874 (26%) had trichomycosis axillaris. In a second population of healthy males, 31 of 113 (27%) individuals had trichomycosis axillaris. In support of hygiene and hyperhidrosis as risk factors, males with trichomycosis axillaris used deodorants less frequently than those without the condition; 1.5% of patients with trichomycosis axillaris also had trichomycosis pubis.)

Shelley, WB, Miller, MA. “Electron microscopy, histochemistry, and microbiology of bacterial adhesion in trichomycosis axillaris”. J Am Acad Dermatol. vol. 10. 1984. pp. 1005-14. (These authors showed that not all Corynebacteria are capable of adhering to the hair shaft. Secretion of a cement-like substance elaborated by the bacteria was proposed to enable bacteria to adhere to the hair shaft.)

Shelley, WB, Shelley, ED. “Coexistent erythrasma, trichomycosis axillaris and pitted keratolysis: an overlooked corynebacterial triad?”. J Am Acad Dermatol. vol. 7. 1982. pp. 752-7. (Two patients with the triad of trichomycosis axillaris, pitted keratolysis, and erythrasma were described. This led the authors to propose the term “corynebacterial triad.”)