Hot tub folliculitis (Pseudomonas Folliculitis, Hot tub rash, Pseudomonas dermatitis)

Are You Confident of the Diagnosis?

Characteristic findings on physical examination

Patients will typically present with follicular-based papules and pustules of the trunk and lower extremities (Figure 1). Excoriated papules and small erosions may be present due to patient manipulation. Rarely are the head and neck involved, as most individuals do not submerge their heads in a hot tub. The rash has been reported to occur anywhere from 6 hours after exposure to 1 week. Itching and tenderness may be associated. Areas of the skin covered by bathing suits are more prone to develop the rash, as is the axilla.

Figure 1.

Hot tub folliculitis due to Pseudomonas.

All patients that have folliculitis should be asked if they have recently used a hot tub, jacuzzi, spa, whirlpool (within the past 2 weeks). If the answer is yes, the clinician must consider this in the differential diagnosis. A patient can be given a sterile specimen container (urine cup) and collect a sample of water from their hot tub for culture purposes.

Expected results of diagnostic studies

No genetic or imaging studies are needed. A Gram stain of the purulent material obtained from a pustule will show gram-negative rods. Biopsy is not required. A biopsy would show a follicular and perifollicular neutrophilic infiltrate. Rupture of the follicular epithelium can be seen, as well as bacteria. Laboratory testing is almost never required, but I will check a complete blood count (CBC) with differential and platelet count if the patient has constitutional symptoms.

If the culture grows Pseudomonas aeruginosa, one should contact the patient and have them initiate disinfection of the hot tub. (See instructions below, in Patient management Section).

Diagnosis confirmation

The differential diagnosis of hot tub folliculitis is small. Acute bacterial folliculitis (most commonly from Staphylococcus aureus) is the major differential diagnosis. There is no clinical means of differentiating the two. For this reason I always culture a pustule from an afflicted patient to determine the correct causative agent. The clinical differential could also include insect bites, but these patients would not have a history of hot tub exposure.

Hot tub folliculitis most commonly occurs after exposure to a contaminated hot tub/spa, but it has also been reported from swimming pools, hydrotherapy pools, water parks and fresh water bodies of water (lakes, rivers, streams). Hot tubs are by far the most common source because the temperatures 98 to 104 degrees F increase the degradation of the chemical disinfectants. The pH and organic load of the hot tub also play a role. Increasing the organic load increases the rate of Pseudomonas colonization of the hot tub. The higher the pH the more likely colonization is to occur. High pH levels make chlorine and bromine less effective.

Heavy use, urine, and contamination from food and leaf debris are the most common contaminants. P. aeruginosa is able to rapidly multiply in hot water once the proper disinfection level of chlorine or bromine has dropped below recommended levels.

Who is at Risk for Developing this Disease?

Any user of a contaminated hot tub is at risk for developing hot tub folliculitis. Persons with more water exposure are at higher risk.

What is the Cause of the Disease?

The ubiquitous gram-negative facultative anaerobic bacteria P. aeruginosa is the causitive bacteria. It causes opportunistic infections. The bacteria is found routinely in soil and water sources, and grows and multiples rapidly in warm water. Improper maintenance of a hot tub can lead to the overgrowth of the bacteria.

The bacteria is capable of producing a variety of pigments, the most well known being pyocyanin, which is a blue-green pigment. It is typically grown in the lab on blood agar, MacConkey agar or Pseudomonas isolation agar. It is lactose negative on MacConkey agar. The bacteria moves by action of a single motile polar flagellum and is approximately 3 micrometers in length. The most frequent serotype of P. aeruginosa isolated in epidemics has been the 0:11 serotype; the 0:9 serotype is a close second. Many other serotypes have been implicated.

The bacterial colonies have a distinct odor of Concord grapes when grown on blood agar or MacConkey agar culture plates.

Humans that are in contact with a contaminated hot tub for longer periods of time are more prone to developing hot tub folliculitis.

Systemic Implications and Complications

Hot tub folliculitis is typically a self-resolving condition, within 1 to 2 weeks, as long as one stays out of contaminated water. Fever, lymphadenopathy, and otitis externa (swimmer’s ear) may also rarely be associated with hot tub folliculitis. Abscess formation has been reported, and immunosuppressed individuals are at a higher risk for developing more severe infections.

Treatment Options

Table 1. Treatment of hot tub folliculitis

Table 1.
Observation – vast majority of cases None Disinfect hot tub
Topical polymyxin B 0.1%    
Application of a topical astringent    
Severe Cases:    
Oral ciprofloxacin 500mg orally twice daily for 7 days    
Other fluoroquinolones    

Optimal Therapeutic Approach for this Disease

When I see a patient with an acute bacterial folliculitis my optimal treatment plan is:

–Culture a pustule.

–Recommend an antibacterial wash (benzoyl peroxide, lever 2000, Dial antibacterial) for 1 month.

–Topical polymyxin B 0.1% twice daily for 10 days to the lesions.

–Avoid topical steroids.

In more severe cases (widespread, unresolved with above washes), I will treat with an anti-staphylococcal antibiotic. Cephalexin 500mg orally twice daily or doxycycline 100mg orally twice daily, until the culture results are back. Once the culture results are in, I will tailor my antibiotic choice to the susceptibility pattern. Currently I am using doxycycline 100mg orally twice daily first line due to the number of cases of MRSA. Therapeutic options for hot tub folliculitis are summarized in the Table.

If a patient has a history of hot tub use and constitutional symptoms, I will treat with ciprofloxacin 500mg orally twice daily for 7 days, and check the patient’s temperature and a CBC. I will follow up with them in 10 days if they have not cleared.

All patients with hot tub folliculitis need to be given information about disinfecting the hot tub. Refer them to the Centers for Disease Control (CDC) website (mentioned in the references).

The vast majority of patients will self resolve with no therapy. Patients should stay out of hot tubs or other water sources (besides showering/bathing) until entirely healed. Those with constitutional symptoms can be treated with ciprofloxacin 500mg orally twice daily for 7 days. The use in children under 18 years is not FDA approved for this indication. In severe cases in the pediatric population, ciprofloxacin may be used, but I would seek the advice of a pediatric infectious disease expert first.

The implicated hot tub must be disinfected. The CDC has written guidelines for publicly run hot tubs and how they should be cleaned and maintained. The CDC recommends a free chlorine level of 1.0ppm with routine hyperchlorination. Hot tubs with jets and “bubble makers” should be hyperchlorinated with these running to cleanse the machinery fully.

Patient Management

Disinfection of the contaminated hot tub is required:

–Drain the water.

–Scrub the reachable surfaces with a household cleanser.

–Refill the hot tub.

–Maintain the pH between 7.2 and 7.8.

–The level of chlorine-based hot tubs should be maintained between 1 to 3ppm

–The level of bromine-based hot tubs should be maintained between 2 to 5ppm

–pH and chlorine/bromine levels should be checked daily.

–Keep the temperature under 104 degrees F.

–Treat with a biocidal shock treatment weekly or more often during times of heavy use (keep jets running to assure all areas are treated).

–Young children should not be allowed in a hot tub (for health reasons and to prevent urine and fecal contamination)

–Cover the hot tub when not in use to keep out environmental debris that may blow into the hot tub.

–Remove bathing suit and shower after each use.

–Change the water every 6 weeks.

–Public pool and hot tub operators should consult the CDC website, for detailed instructions.

Unusual Clinical Scenarios to Consider in Patient Management

Hot tub folliculitis most frequently is an isolated disease; however, it can cause epidemics. Many have been documented in the past. If one encounters multiple patients who have Pseudomonas folliculitis with a common source, local and state health officials should be contacted to perform an epidemiologic analysis.

Rarely the lesions have been described as vesicular. I have never seen this and I question if this is correct.

Cases of Pseudomonas folliculitis have been reported after the use of contaminated wet suits, bathing suits, and sponges.

Some cases are associated with constitutional symptoms including fevers, chills, myalgias, headaches, lymphadenopathy, and otitis externa.

Involvement of the areola Montgomery glands has lead to significant breast tenderness.

CBC will rarely show a leukocytosis, with a left shift.

Not every individual that gets exposed to the bacteria, even for prolonged periods, develops the disease. Possible explanations include intact skin or an unknown host response to the bacteria. Infection may require small portals of injury to the skin to gain a foothold. One possible explanation may be shaving (which causes tiny microabrasions), although this would tend to indicate that females would be more prone to developing the disease, which they are not.

Immunosuppressed patients, and patients with chronic skin diseases (which increase the portal of entry) should be warned about the possibility of this disease. If they wish to have a hot tub, they should contact their physicians, and my recommendation would be that they strictly keep thier hot tub at the correct pH and disinfectant levels. This is accomplished by daily testing of pH and chlorine or bromine levels.

Hot foot syndrome or hot hand and foot syndrome can be considered when the lesions are isolated to the palms and soles. Please see that chapter for more in-depth details.

Pseudomonas folliculitis has been reported after depilation. This occurs within 2 days of hair removal, most frequently after wax removal, but also has been reported after electrolysis. The bacteria is either on the skin at the time of hair removal, or was accidently placed there druing the procedure (contaminated wax, etc).

Gram negative folliculitis, seen after the use of chronic oral antibiotics, may reveal P. aeruginosa. This is explained in more detail in the gram-negative folliculitis chapter.

Hot tub folliculitis has been reported in an individual using a contaminated sponge to wash their legs.

As an interesting aside, being an avid aquarium keeper, I well know that P. aeruginosa is present in all tropical fish tanks and can cause fish, snail and plant disease. I have had many fish infected with this bacteria and most succumb to the disease. I could find no reports of this bacteria causing human disease after exposure to a fish tank. This is likely because tropical fish tanks are kept between 70 to 80 degrees F, which is below this bacteria’s optimal growth temperature. Most aquarists also take precautions to avoid contacting the water for prolonged periods of time through the use of rubber gloves when cleaning thier tanks.

What is the Evidence?

Zacherle, BJ, Silver, DS. “Hot tub folliculitis: A clinical syndrome”. West J Med. vol. 137. 1982. pp. 191-4. (One of the initial reports of hot tub folliculitis. Reports a case and reviews the disease. Discusses the pathomechanism and therapeutic options.)

Baron, EJ. “Rapid identification of bacteria and yeast: Summary of a national committee for clinical laboratory standards proposed guidelines”. Clin Infect Dis. vol. 33. 2001. pp. 220-5. (Thorough review of bacterial identification by various laboratory methods. Describes the characteristics of Pseudomonas bacteria when grown on various culture media. This reference is a guide for microbiology and does not discuss clinical diseases.)

Yu, Y, Cheng, AS, Wang, L, Dunne, WM, Bayliss, SJ. “Hot tub folliculitis or hot hand-foot syndrome caused by Pseudomonas aeruginosa”. J Am Acad Dermatol. vol. 57. 2007. pp. 596-600. (Report of an outbreak of 33 children who developed signs and symptoms of both hot foot-hand syndrome and hot tub folliculitis after exposure to a contaminated pool.)

Silvestre, JF, Betlloch, MI. “Cutaneous manifestations due to Pseudomonas infection”. Int J Dermatol. vol. 38. 1999. pp. 419-31. (Excellent review of pseudomonal skin infections. Starts with an overview of the bacteria and discusses each and every type of Pseudomonas skin infection.)