Definition

Apocrine miliaria is a chronic inflammatory skin condition believed to occur when sweat ducts become blocked or inflamed. It is recurrent and potentially lasting for years. George Henry Fox and John Addison Fordyce first identified it in 1902, and it is more commonly referred to as Fox-Fordyce disease.

Causes

The exact cause of apocrine miliaria remains unknown. Blockage of sweat glands, caused by the accumulation of dead skin cells in hair follicles, is considered a possible mechanism for forming miliaria.

Some factors believed to trigger apocrine miliaria include:

• Genetic predisposition: Although not usually inherited, rare cases of apocrine miliaria have been reported among siblings.
• Hormonal influence: Apocrine miliaria typically appears after puberty and rarely before or after menopause. The influence of hormones is supported by its recurrence before menstruation and improvement during pregnancy, post-menopause, or with contraceptive use.
• Laser hair removal: Apocrine miliaria has been linked to hair removal procedures, where laser radiation damages hair follicles, leading to an accumulation of dead skin cells that block sweat glands. Multiple laser sessions have also been associated with thermal damage to hair follicles, contributing to the condition.
• External factors: Stress, sweating from exercise, and hot and humid weather can trigger itching, which leads to the onset of apocrine miliaria.
• Excessive sweating: Caused by physical activity, humid climates, heavy clothing, sexual activity, or emotional stress, which can exacerbate flare-ups.

Risk factor

Most cases of apocrine miliaria occur in young women post-puberty. About 90% of cases are found in women aged 13 to 45, with an average onset age of 21. The female-to-male ratio is 9:1. Though generally not influenced by ethnicity, some studies suggest a higher prevalence in Jewish populations.

Symptoms

Symptoms include intense itching and rash. When sweat ducts are blocked, sweat accumulates beneath the skin, causing the glands to rupture, which leads to inflammation and severe itching. This sensation is often heightened by sweating, stress, anxiety, and nighttime, potentially disturbing sleep. In some cases, itching may not be present.

Itching often precedes the appearance of the rash, typically found in areas rich in sweat glands such as the armpits, around the nipples, and genital and anal regions. Less commonly affected areas include the navel, the space between the genitals and anus, and the inner thighs. Rarely, the lips, chest, abdomen, and limbs are affected. Apocrine miliaria usually affects both sides of the body.

The rash consists of multiple small, firm, dome-shaped nodules with a shiny surface ranging from 2 to 3 millimeters in size. The color may vary from skin-coloured, yellowish, reddish, pink, or light purple. If punctured, the nodules may release yellowish or milky fluid.

Diagnosis

Diagnosis is usually based on a physical examination, but additional tests may include:

• Examination of the rash: Checking for inflamed hair follicles or damaged hair and comedones.
• Biopsy: A biopsy of the nodules confirms the diagnosis, especially when physical examination alone is inconclusive.
• High-definition optical coherence tomography imaging: Used in cases where a biopsy does not yield a definitive diagnosis.

Management

Treatment for apocrine miliaria can be challenging due to limited studies. However, therapy is crucial to alleviate intense itching. Several options include topical medications, oral drugs, and surgery.

First-line treatments include topical retinoids, benzoyl peroxide, clindamycin, corticosteroids, calcineurin inhibitors, and oral contraceptives. These are preferred due to their availability, ease of application, and minimal serious side effects, though the optimal regimen remains unknown. Relapses may occur after stopping treatment.

• Low-potency corticosteroids: Applied twice daily until symptoms improve, then reduced to twice or thrice weekly.
• Topical clindamycin: Applied twice daily for 4 weeks, with improvement typically seen within the first few weeks.
• Benzoyl peroxide 5%: This antiseptic is used daily for up to 8 weeks.
• Topical calcineurin inhibitors: Reduce inflammation without causing skin thinning, such as pimecrolimus and tacrolimus, used twice daily for 8 weeks and possibly as maintenance therapy.
• Topical retinoids: Tretinoin and adapalene may reduce follicular blockage but can cause skin irritation, which may require reducing usage to every other day.
• Isotretinoin: Prescribed in severe cases.
• Antihistamines: To alleviate itching.

For more severe cases or those unresponsive to initial treatments, second-line options include:

• Surgical removal of apocrine miliaria
• Fractional laser treatments
• Pulsed dye laser
• Botulinum toxin injections
• Phototherapy
• Electrocoagulation
• Dermabrasion
• Copper vapor laser
• CO2 laser
• Liposuction-assisted curettage
• Microwave technology

Nevertheless, relapses frequently occur after treatment cessation.

Complications

Chronic apocrine miliaria may result in thickened, rough, and darkened skin from repeated scratching. In severe cases, gland and follicle damage may lead to a lack of sweating and hair in the affected areas.

The condition can persist for years. In some cases, it resolves during pregnancy, while others may experience improvement after menopause, although some continue to suffer post-menopause.

Prevention

Preventing recurrences involves avoiding hot environments and situations that induce sweating. Hormonal therapy has been suggested, though its benefits are still uncertain.

When to see a doctor?

If you experience symptoms of apocrine miliaria, particularly itching, it’s advisable to consult a doctor for symptom control and to prevent recurrence.

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