What is Fox-Fordyce disease?

Fox-Fordyce disease, also known as apocrine miliaria, is a chronic inflammatory skin disorder which affects the apocrine glands.¹ These are exocrine glands found in areas of the body, including the armpits, the anogenital area and the mammary glands, and they are associated with hair follicles. They secrete a thick, oily substance which aids in regulating the temperature of the body.² Fox-Fordyce disease presents as a red raised rash in a linear pattern in areas with a lot of apocrine glands, like the armpits, areolae and anogenital region.¹

(3) Apocrine Gland [Internet]. Animalia-life.club. 2024 [cited 2024 Aug 12]. Available from: https://animalia-life.club/qa/pictures/apocrine-gland

What causes it?

It is believed to be caused by a blockage of the apocrine sweat glands by keratin accumulation in the funnel in which a hair follicle grows. This idea is supported by recent incidents of Fox Fordyce disease being brought on by laser hair reduction, as these cause follicular damage.
Other potential sites of blockage are in the intraepidermal (within the epidermis) portion of the apocrine sweat duct by detached apocrine secretory cells. Hormonal, physical and environmental factors can also play a role in the development of the disease, such as increased sweating, exercise, humid climate, emotional stress, tight clothing and sexual activity.

As Fox Fordyce disease is most common in people assigned female at birth (AFAB), it suggests a hormonal component. Patients are rarely symptomatic before puberty, symptoms worsen around menstruation, worsen or improve in pregnancy and cease during menopause. Androgen hormones like testosterone fluctuate throughout a woman's menstrual cycle, and these hormones can alter skin healing and sweat composition, which can lead to an inability of glands to secrete oil, which leads to a blockage as well as glandular rupture and dermal inflammation. Rashes caused by Fox Fordyce disease are often itchy, and this is due to a leakage of glandular content. When a person scratches the rash, this leads to bumps on the skin.¹

How common is it?

The exact prevalence is unknown due to how rare the disease is.¹

How is it diagnosed?

Diagnosis is usually made by an examination of the rash. On occasion, a skin biopsy may be carried out in order to confirm the diagnosis. This is where a small sample of the skin is taken by a needle so it can be examined under a microscope.⁵

How is it treated?

There are a variety of different treatments that may be used, including:

• Topical steroids can help relieve itching. However, these can not be used continuously as they can cause the skin to become thin
• Topical calcineurin inhibitors can also be used to calm itching
• Topical retinoids like tretinoin can be used to reduce the rash
• Topical antibiotics like clindamycin

There are also oral treatments that can be employed:

• Antihistamine tablets can be used to control the itching
• An estrogen-based oral contraceptive pill may be prescribed in women with Fox Fordyce disease to alter hormone levels; however, when you stop taking the pill, the rash may come back
• Oral isotretinoin can also improve symptoms

Other options also include:

• Treatment with botox either to help relieve the itch caused by the condition or to stop excess sweating, which can serve as a trigger for the condition
• Surgery can also be used⁶

What's the prognosis?

At present, there is no absolute cure for Fox Fordyce disease, but improvement of symptoms and a complete healing of the affected area has been reported, which means the overall prognosis is quite favourable.⁵

Conditions associated with Fox Fordyce

There are a number of other skin conditions that are associated with Fox Fordyce disease and which are considered when making a differential diagnosis. These include:

• Folliculitis
• Milia

What is folliculitis?

Folliculitis is a very common skin condition which is usually caused by the infection or inflammation of the hair follicle. This leads to the formation of small bumps on the skin that contain pus, as well as red bumps on skin that is covered by hair. It is not a life-threatening condition and often heals on its own, but in people who are immunocompromised, it has the potential to progress to a more serious disease.

What causes it?

Folliculitis is often caused by a bacterial infection of the superficial or deep hair follicle. It can also be caused by fungal species and viruses. 

Some of the causative agents for folliculitis include:⁷

• Staphylococcus aureus, a bacterium found on the skin and in the nose of 30% of people.⁸ This is the cause of the most common form of folliculitis, superficial bacterial folliculitis
• Pseudomonas aeruginosa, a gram negative bacteria. This type of folliculitis usually arises after exposure to contaminated water from improperly treated swimming pools or hot tubs, earning it the name “hot tub” folliculitis
• Malassezia is a species of fungi. This causes pityrosporum folliculitis, which is commonly found in adolescence due to the increased activity of the sebaceous glands. It is often found on the shoulders, back and neck
• Herpes virus. This presents similarly to bacterial folliculitis except that there will be both small solid elevated bumps and fluid-filled blisters. The lesions will also appear in groups of clusters

How common is folliculitis?

People with a history of diabetes, obesity, prolonged use of oral antibiotics, those who are immunocompromised, as well as those who shave frequently, are at a risk of developing the condition.⁷

How is it diagnosed, and what's the prognosis?

Most of the time, no diagnostic testing or radiographic evaluation is needed; a doctor will be able to diagnose the condition based on gathering a thorough history of the person they are treating and performing a physical exam in order to assess the rash. A potassium hydroxide preparation can be used to visualise hyphae and spores that are associated with folliculitis caused by Malassezia.

The condition is often non-cancerous and self-limiting, meaning it will resolve on its own without the need for treatment, so the prognosis is very good for a full recovery. Proper hygiene practices and managing underlying conditions that may have led to the infection will prevent it from coming back.

How is it treated?

Different types of folliculitis will be managed differently.

Staphylococcal folliculitis often will resolve on its own in a few days, but if it becomes chronic, topical antibiotics like mupirocin can be used.

• Gram-negative folliculitis will also often resolve between 7-10 days if good skin hygiene practices are employed. If not, oral antibiotics like ampicillin can be used
• Pityrosporum folliculitis can be treated with oral antifungal agents like itraconazole and fluconazole.
• Viral folliculitis is treated in the same way you would treat a herpes outbreak, with oral acyclovir, valacyclovir and famciclovir⁹

What is milia?

Milia are non-cancerous and transparent keratin cysts that look like small, firm, white raised lesions. They are most commonly found on the face but can also be found on the chest and upper back, arms and legs and the genital area. Most milia are primary congenital milia, meaning they appear spontaneously and are present at birth. There is also primary milia, which occurs due to inherited genetic skin disorders. Secondary milia occur due to skin conditions or skin trauma, as well as a side effect of taking medication.

How common is milia?

Primary congenital milia occur in up to 40-50% of healthy newborn babies.¹⁰

What causes it? 

Primary milia is linked to specific inherited genetic disorders, including oro facial digital syndrome 1 . Secondary milia occurs as a result of trauma such as dermabrasion or radiotherapy.

How is it diagnosed, and what is the prognosis?

Milia lesions are diagnosed based on physical examination. Sometimes, an incision and drainage of the keratinous content of milia may be used to confirm a diagnosis, but this is rare. 

Congenital milia tend to resolve spontaneously without any scarring within a couple of weeks, and they usually disappear within the first month of life. Acquired milia may continue without treatment.

How is it treated?

Congenital milia do not need any particular kind of treatment as they resolve spontaneously. Other forms of primary milia as well as secondary milia may not resolve on their own and so can be treated with simple surgical intervention like evacuation with a tiny incision with a scalpel blade and applying pressure with a comedone extractor or curette. Other treatments that are available also include the use of topical retinoids, electrodesiccation or electrocautery.¹⁰

Summary

In summary, Fox Fordyce disease is an inflammatory skin disorder that causes a red rash to appear on the skin. It is caused by a blockage of sweat glands that can be brought on by laser hair removal, hormones and other environmental factors. It is associated with other skin conditions, including folliculitis and milia. Folliculitis is an infection of the hair follicle that causes red bumps on the skin and can be caused by bacterial infection. Milia is a skin condition that causes keratin cysts. It can be brought on by inherited genetic disorders or trauma.